sharply-keeled in this shell, which is, moreover, remarkably distinguished from all the allied forms, by the division of the inferior digitation into two distinct processes; one of these is prolonged downwards in a direction nearly continuous with the channel, and the other is recurved upwards. As eight or nine similar specimens have been found, the bifurcation of the inferior digitation is, in all probability, a specific character; if this should prove to be the case, I propose to distinguish the species by the name of the assiduous and accurate observer by whom it was first discovered. The figure shows the dorsal aspect of the shell. § 15. ANCYLOCERAS, FROM ATHERFIELD.-Among the treasures obtained from the same locality by Mr. Beckles, is a spendid example of one of the most elegant shells of LIGN. 41-ANCYLOCERAS MATHERONIANUS D'ORBIGNY.-4th Nat. size. (In the cabinet of S. H. Beckles, Esq.) the elongated type of cephalopoda that occurs in the cretaceous formation; it is a species of ancyloceras, a genus related to scaphites, but characterised by the turns of the spire or coil being distant from each other, while in the latter they are in close contact, and by other well-marked peculiarities. Fine specimens of Scaphites gigas (Pl. V., fig. 11,) have for some years been occasionally obtained from Atherfield, but this beautiful allied form was previously * Paléontologie Française; terrains crétacés, Pl. CXXII. unknown in the British strata. Several examples have been discovered in France, and the species is figured and described by M. D'Orbigny, with the above specific name, in honour of M. Matheron, who first collected this shell at Cassis, Bouches-du-Rhône. * This fossil is about nine and a half inches long, and of an oblong form; its spire is composed of two or three distinct coils, which occupy about one-fourth the entire length of the shell; it is traversed obliquely by prominent ribs, each bearing six tubercles, which are the bases of spines; between each tuberculated rib there are three or four small smooth intermediate ones. The aperture of the shell is oval; the rows of turbercles form three distinct series on each side; the back or keel is rounded, with a row of tubercles on each margin, as shown in the upper figure, which represents a portion near the spire. The specimen is a very sharp cast, which in some parts is covered by the remains of the shell. § 16. PHOSPHATIC CRETACEOUS BEDS,† Molluskite.The occurrence of the mineralised remains of the soft bodies of the mollusca whose shells occur in the firestone and greensand strata, either in amorphous masses, or as casts filling up the cavities of shells, is noticed in p. 181, and reference made to a more detailed account in the "Medals of Creation." The layers of firestone, or upper greensand, forming a junction with the galt, abound in these fossils; and this fact was pointed out in 1822, in my "Fossils of the South Downs;" in Hants, Kent, and Surrey, the lowermost bed of galt, in contact with the greensand below, is equally rich in similar remains. These *Such also is the case in Turrilites tuberculatus; that the tubercles on the casts are merely the bases of spines, may be seen in specimens in my cabinet. †The name given by Capt. Ibbetson, Mr. Nesbitt, and others, to the strata abounding in molluskite and phosphate of lime. beds of molluskite are very persistent, and may be traced through Sussex, Surrey, Kent, and Hampshire, and in the Isle of Wight along the Undercliff. The same fossils also occur abundantly in some of the strata or chalk marl above, and of the greensand below the galt. Molluskite has lately been in much request for agricultural purposes, the large quantity of phosphate of lime it contains rendering it a valuable manure for certain soils. A Memoir "On the Position in the Cretaceous Series of Beds containing Phosphate of Lime" has been published ;* and Mr. Nesbitt has analysed hundreds of specimens to show the proportionate quantity of phosphate of lime in particular nodules and beds. The first notice of these substances in the upper greensand strata at Farnham was announced as the discovery of a bed of fossil guano, and great expectations were raised that it would prove an inexhaustible mine of wealth. At the present time (1851) many persons are engaged on the summit of the hill above Blackgang in extracting the casts of ammonites and other shells, and the nodular masses of molluskite, from the arenaceous green marl that crops out from beneath the upper chalk along the heights of the escarpment of the Undercliff; the loose rubble, it is said, is rejected, probably because analysis has shown that the casts of ammonites, &c., contain the largest proportion of phosphate of lime; for in Mr. Nesbitt's tables of phosphoric acid in nodules and casts of shells from St. Catherine's Downs, the casts are stated to contain from 40 to 50 per cent. of phosphate of lime, while the surrounding greensand, or hassock, yields but from 2 to 10 per cent. Probably the combination of the calcareous earth, filling the shell, with the phosphoric acid derived from the soft parts of the mollusks has imparted this excess to the casts. The Government Geological Survey of the Island, which is "Geological Journal," vol. iv. p. 257. now in progress, will doubtless give detailed information respecting the extent, position, and chemical constituents of these deposits.* It is worthy of remark, that the presence of phosphoric acid is not confined to deposits teeming with the remains of animal structures: traces of it occur even in volcanic rocks. Dr. Fownes detected its presence in igneous rocks * I cannot refrain from inserting the following humorous notice of the "Phosphate Diggins' " from the Hants Indepen dent : "ANOTHER CALIFORNIA.-A speculation has been recently entered into, and is in active operation at the back of the Island, by some enterprising individuals from the metropolis, which has been an object of extreme wonderment to the natives for these last few weeks, more particularly to those who reside near the spot in question; and if the object sought for by these parties, much of which has already been obtained, is not rich in the precious metal which distinguishes the quartz of California, they must entertain the idea of speedily transmuting it into gold, if they intend to defray the immense cost of procuring it. In order to enlighten our readers as to the circumstances which have come to our knowledge relating to this matter, we must remind them that on the edge of the High Uppercliff, which extends from Blackgang to Ventnor, there creeps out at intervals a stratum of fossils; one of these, situate exactly over that wild-looking spot at the back of the celebrated Chalybeate spring, has been long known to the fishermen on the coast as abounding in the most perfect specimens, but excepting a pecuniary reward for the discovery of an extraordinary antediluvian monster from some curious geologist, it was never imagined or suspected that it possessed the slightest monetary value as an article of commerce. Such, however, proves to be the fact, if we may judge of the labour which is engaged to procure it. Some scientific explorer of our island treasures having carried back with him to London a specimen of these fossils, an analysis of their component parts warranted the expenditure of vast sums of money in order to procure more; and for the last three weeks great numbers of labourers, their wives and children, have been employed daily, the former in removing the upper soil and digging up the required material, the latter in picking and sifting it, preparatory to its being exported, for which preparations of all ages, and was so struck with its occurrence in ancient lavas, &c., that he remarked: "It cannot be devoid of interest to trace to its first source the enormous quantity of phosphoric acid, now for the most part locked up in a temporarily insoluble condition in the vegetable and animal kingdoms, and in the various strata of calcareous and are now making. The article for which they are searching is chiefly composed of fossil ammonites, and the veins of strata in which they lie are from one to three feet in thickness. The shells themselves vary in size from the dimensions of a hazel-nut to the diameter of a common dinner-plate, but we saw a specimen dug from this spot not long since which was as large as the top of a tea-table. The most perfect shells are preserved for the cabinets of the curious; the broken pieces, which now amount to several tons weight, are carefully separated from the extraneous matter, and placed by themselves in a heap ready for exportation. The spot is strictly guarded, not only on the working days, but more particularly on the Sabbath. The utmost secrecy is observed by the principals as well as the overlookers, as to the use to which it is intended to apply the collection, and no interrogations whatever can elicit a satisfactory answer. When the diggins' first commenced, this singular stratum 'cropped out' near the surface, and was easily to be procured, but as the labourers proceed further into the side of the hill, they are obliged to remove the upper crust of loam and limestone, which is from six to ten feet in thickness, before they can arrive at the fossil strata. The land is in the possession of Mr. William Henry Dawes, and we are informed that the parties have agreed to pay him £30 per acre for liberty to turn over the surface and extract the fossils! We have been informed that this same stratum extends to Ventnor, and shows itself on Bembridge Down. We have not yet met with a practical chemist who can explain its component parts, but we suspect it will be found to contain a portion of phosphate of lime, and that it will form the principal ingredient in the manufacture of artificial manures. That it is of considerable value, no one can doubt who has witnessed the cost of procuring it; and we invite a controversy on its merits, as we cannot help feeling somewhat chagrined that this interesting discovery should have been made by utter strangers, who are likely, if there be a profit attending it, to reap the benefit thereof." |