(Jhemical (■uiiipositwii uf Rcceiil and Fossil Liugul;e. 337 

 then as follows : — 



Phosphate of lime . . -0978= 85*79 per cent. 

 Carbonate of liiiic . . •0134= Wlo 

 Magnesia -0032= 2-80 



•1141=100-34 



The proportion of phosphate of lime is that contained in 

 human bones after their organic matter has been removed. 



The texture of the ancient Linyuhe v/as observed to be unlike 

 that of most other fossil shells, being more or less dark brown in 

 colour, brilliant, almost ojjake, and not at all crystalline. These 

 characters are also found in the allied genus Orbicula, and we 

 therefore examined an undescribed species of it from the Trenton 

 limestone, beautifully marked in a manner resembling Conularia 

 granuluta, and another large species, also undescribed, from the 

 Upper Silurian ; both of these consist chiefly of phosphate of 

 lime ; and the shell of a recent species, 0. lanieUosu, from Callao 

 was found to be similar in composition. We have not yet been 

 able to examine a specimen of the genus Obolus. The same dark 

 colour and brilliancy were also remarked in the genus Cumdaria, 

 and the shell of C. trentonensis proved on examination to be 

 composed in like manner of phosphate. 



The similarity of eomj)osition in these genera is in accordance 

 with the acute observations of Mr. Hall, who iinds that Cunu- 

 lui'ia is almost always associated with Lingula and Orbicula, and 

 remarks that "these shells, so unlike in structure and habit, 

 appear to have flourished under similar circuinstances, and to 

 have required the same kind of ocean bed or sediment " (Palae- 

 ontology, vol. i. p. 101). 



For the sake of comparison we have examined the following 

 fossil shells ; they have a common character, distinct from those 

 already described, being lighter coloured, more translucent and 

 granular in texture : Atrypa eaians, Leptana alternata, and Orthis 

 pecteiiella from the Trenton limestone ; 0. erratica from the 

 Hudson River group, and Clionctes lata ? from the Upper Silu- 

 rian, besides Isotelus yigas, and a species of Cythere from the 

 Trenton. All of these consist of carbonate of lime, with only 

 such traces of phosphate as are generally found in calcareous 

 shells. 



In the Report already quoted we have given a description of 

 some phosphatic bodies which resemble the coprolites of the 

 calciferous sandstone, and are found at Riviere Quelle in thin 

 layers of a conglomerate limestone, which is intcrstratitied with 

 red and green shales, and belongs to the top of the Hudson 

 River group, or the base of the Oneida conglomerates. The 

 phosphatic nrasses are very abundant, and rounded, flattened, or 



Phil. May. S. 4. Vol. 7. No. 1(5. May 1854. 2 A 



