1891.] MR. G. A. BOULENGER ON CHELONIAN REMAINS. 7 



p. 15, R. 1499) comes nearest the existing T. hurum. Gray ; for the 

 skull which I now exhibit agrees in almost every respect with that 

 of the Indian T. hurum, of which a specimen of the same size (half- 

 grown) is figured for comparison (fig. 4). This is very remarkable, 

 species of Trionychoids being so well characterized by their skulls ; 

 and had the fossil been obtained from the Pleistocene of India, I 

 should have unhesitatingly pronounced it to belong to T. hurum. 



Four species appear to be well distinguished, from their shells, in 

 the Hordwell beds, viz. : — T. harbarce, Ow., T. henrici, Ow., T.incras- 

 satus, Ow., and T. planus, Ow., the latter species being only known 

 from the posterior portion of the carapace. It is just to this species 

 that I should feel inclined to refer the skull, as it is the only one 

 which, in the coarse sculpture of its dorsal plates, at all approaches 

 the existing T. hurum ; and I am pleased to find that Mr. Lydekker 

 expresses the view that the mandible alluded to above may possibly 

 be referable to T. planus. It is, however, not possible to ascertain 

 whether in the species with very coarse sculpture of the dorsal shield 

 (T. planus) two neural plates instead of one are present between the 

 first pair of costals, as in the Indian group to which T. hurum 

 belongs ; let us hope that future finds may settle this point. 



In the meanwhile, this fossil skull (see fig. 5, p. 6), may be provi- 

 sionally referred to T. planus, Owen. 



3. On a Humerus of Eosphargis gigas, Owen, from the London Clay 

 of the Isle of Sheppey, Kent. 



The proximal end of the left humerus of an Athecan Turtle from 

 the London Clay (Lower Eocene) of Sheppey, presented by J. 

 "Wickham Flower, is preserved in the Museum of the College of 

 Surgeons, and was described by Owen (Descr. Cat. Foss. Rept. 1854, 

 p. 3) as " the lower or distal end of the tympanic bone of the Croco- 

 dilus toUapicus ^ ; it exceeds in size the corresponding part of the 

 largest recent Crocodiles in the Hunterian Collection " ^ This 

 specimen may be safely referred to Lydekker's Eosphargis gigas, Ow,, 

 but belongs to an individual considerably smaller than any on record, 

 the greatest diameter of the proximal end of the humerus being only 



^ On this occasion, I would observe that C. toUapicus, Ow. ( = C. spenceri, 

 Buckl., = G. champsoides, Ow.), is no true Crocodilus, as it differs in its dental 



formula ( ■ Crocodilus hsiymg — r^— )> the absence of a pointed process on 



the free border of the quadratojugal, and the large size of the mandibular 

 vacuity, in all these characters agreeing with Biplocynodon, to which genus the 

 British Upper Eocene and Oligocene Crocodile Alligator hantoniensis, Wood 

 (^= Crocodikis hasting site, Ow.), belongs. I regard Biplocynodon spenceri and 

 D. hantoniensis as standing in the same relation to each other as the recent 

 Crocodilus intermedius and C. palustris. We therefore know of no British 

 Eocene or Oligocene Crocodilus, the remains hitherto referred to that genus 

 belonging to Biplocynodon. 



^ Two other fossils are referred by Owen (1. c.) to the same Crocodile. His 

 "portion of the left ramus of the lower jaw " I regard as a portion of scapula 

 of Eosphargis ; and his " another portion of the right ramus of the lower jaw " 

 belongs to a Liassic Plesiosaurian. 



