Zoological Society. 501 



labio externo crassiusculo, intus obsolete denticulato ; labio interno 

 intus tuberculo obtuso instructo ; canali brevi. 

 St. Vincent's ; the late Rev. L. Guilding. 



Columbella atomella, Duel., Thes. Conch, pi. 40. f. 184, 185. 



Col. testd oblonyd, albicante, nonnunqudm pallide castaneo-unifas- 



ciatd, spird acuminatd ; anfractibus 6, longitudinaliter costatis ; 



suturd crenatd; ultimo anfractu antice lavi, supra canalem trans- 



versim sulcato ; aperturd august d. 

 West Indies ; Rev. L. Guilding. 



March 26. —The Right Hon. William Sturges Bourne in the Chair. 



A communication was made by Dr. Falconer, conveying the 

 substance of a paper by Capt. Cautley and himself on the osteolo- 

 gical characters and palseontological history of the Colossochelys 

 Atlas, a fossil tortoise of enormous size, from the tertiary strata of 

 the Sewalik hills in the north of India — a tertiary chain apparently 

 formed by the detritus of the Himalaya mountains. 



A great number of huge fragments, derived from all parts of the 

 skeleton except the neck and tail, were exhibited on the table, illus- 

 trative of a diagram by Mr. Scharf of the animal restored to the 

 natural size. 



The communication opened with a reference to the reptilian forms 

 discovered in the fossil slate, among which colossal representatives 

 have been found of all the known tribes, such as the Iguanodon, Me- 

 galosaurus, Labyrinthodon, &c, besides numerous forms of which no 

 living analogues exist, such as the Enaliosaurian reptiles and Ptero- 

 dactyles. No fossil Testudinata remarkable either for size or devia- 

 tion from existing forms, have hitherto been found in the fossil state. 

 The Colossochelys supplies the blank in the first respect, while it 

 differs so little from the land-tortoises in the general construction 

 of its osseous frame as hardly to constitute more than a subgenus 

 of Testudo. 



The plastron or sternal portion of the shell affords the chief di- 

 stinctive character. The episternal portion in the adult is six and a 

 half inches thick, and contracted into a diameter of eight inches, bifid 

 at the apex, €ind supplied with a thick cuneiform keel on its inferior 

 side : this keel constitutes one of the principal features in the fossil. 

 The entosternal portion exhibits exactly the form of Testudo, the 

 same being the case with the xiphiosternal or posterior portion. The 

 plastron in the adult animal was estimated to be nine feet four 

 inches long. 



The carapace or buckler of the shell coincides exactly with the 

 general form of the large land-tortoises, of which it exhibits only a 

 magnified representation, flattened at the top and vertical at the sides, 

 with the same outline and recurved margin. The shell was estimated 

 to have been twelve feet three inches long, eight feet in diameter, 

 and six feet high. 



The extremities were described as constructed exactly as in the 

 land-tortoises, in which the form of the femur and humerus is marked 

 by peculiar characters. These bones in the fossil were of a huge 



