APPENDIX TO THE CATALOGUE OF SHIELD REPTILES. 



in the skull, between the end of the maxilla and the tym- 

 panic bone. Nose flattened, with a deep longitudinal groove. 

 Chin with one, central beard. 



Podocnemina, Gray, P.Z.S. 1870, p. 719. 



" It has been well observed that after the greatest care 

 some new fact in the structure of an animal that has been 

 often observed will occur. I have been for several years 

 collecting together the species of Tortoises, and more espe- 

 cially studying the osteology, and particularly the skulls of 

 the Testudinata ; I have published several papers on them, 

 and have collected these papers together, with many addi- 

 tional observations and descriptions, as a 'Supplement to the 

 Catalogue of Shield Reptiles in the British Museum,' which 

 is printed and ready for distribution ; and yet, before it has 

 actually been published, an accidental circumstance has re- 

 vealed to me that a series of specimens that I believed were all 

 of one species, coming from nearly the same locality, consists 

 of two most distinct species, belonging to two most distinct 

 genera, marked by very great differences in the form of the 

 alveolar process, which has been confirmed by the exami- 

 nation of the skulls or heads of a series of specimens of each 

 species of different ages. 



" Mr. Edward Bartlett, during his excursion to Brazil for 

 the purpose of collecting objects of natural history, sent to 

 the Museum a series of specimens of a freshwater Tortoise 

 which he obtained in the freshwater lakes in the region of 

 the Upper Amazons. They were considered to be half- 

 grown examples of Podocnemis expansa, which they greatly 

 resemble in all external characters ; but on Mr. Edward 

 Gerrard, junior, preparing a skeleton of one of them for 

 the collection, it was discovered that it possessed a very 

 different alveolar surface of the upper jaw ; and on examin- 

 ing the jaws of the other specimens, they were all found 

 to have the same peculiar character ; therefore I have de- 

 scribed and figured these jaws ; and to point out, in the 

 shortest manner, the differences between it and the other 

 genera of the family, I have formed a tabular distribution 

 of them. 



" In the skulls of all the genera in this family the vomer is 

 not ossified ; and the internal nostrils of the skull are not 

 divided by a septum, but leave a large open aperture in tin; 

 front of the palate. 



" The bony vaulted arch that covers more or less com- 

 pletely the depression on the side of the skull for the tem- 

 poral muscle, is entirely formed, according to Prof. Owen, 

 of an extension of the parietal bone. 



"In my paper on the genus Podocnemis in the 'Proceed- 

 ings' of the Society I pointed out that the Podocnemis ex- 



pansa of Wagler and the Emys expansa of Cuvier, which had 

 been considered the same species, had very different skulls, 

 and, entering into the details of the differences between 

 them, I formed them into separate genera. 



"In Bartlett ia and Podocnemis < ipmtxn both the ischiadic 

 and iliac bones are affixed by a bony suture to the sternum. 



'• The thorax of the animals of this family has the cavity 

 contraeted, like the shells of the greater part of the Bata- 

 gurida; of India. In a very large specimen of Podocni mi 

 expansa the front contraction is separated from the margin 

 of the cavity by a considerable space, and may be so in 

 younger specimens ; in the genus Barilettia it is continuous 

 with the margin of the cavity, as in all the Batagurs I have 

 examined." — P. Z. S. 1870, pp. 718, 719. 



Spix first observed these Tortoises had only one chin- 

 beard; he particularly describes Emys amazoniea, t. 1, :is 

 " guli'i unieirrhosa ; " but E. eryihrocepJiala he describes as 

 " gula non cirrhosa " — which, if not a mistake, is unknown 

 to me. 



2. CHELONEMYS. 



Head elongate ovate ; the alveolar surface of the upper 

 jaw rather sinuous, convex in front and shelving behind, 

 with two diverging ridges, separated by a broad longitudinal 

 depression, the inner one low and indistinct. Lower jaw 

 with a sharp outer edge and a deep longitudinal concavity, 

 the inner margin elevated, divided by a central longitudinal 

 groove into two ridges ; the central notch produced for- 

 ward between the under margins towards the apex of the 

 beak. (Cuvier, Oss. Foss. v. part 2, pi. 11. figs. 11, 12.) 

 Tympanum moderate. 



Chelonemys, Gray, P. Z.S. 1S70, p. 719. 



Cheloneinys Dtuneriliana. 



Gray, Suppl. Cat. Sh. Sept. p. 83; P.Z.S. 1870, p. 71!'. 

 Podocnemis uuifilis, Troschel in Schomburgk, llcise in Beit. 

 Guiana, vol. iii. p. 647. 



Gray, Ann. <$■ Mag. N.II. 1871, vol. viii.p. 68; P.Z.S. 

 1871, pp. 745, 747, f. 2 (tympanum). 



" A freshwater Tortoise from Guiana was thus described 

 in 1848:— 



" ' Podocnemis unijilis, Troschel, n. s. (Schomburgk. Reise 

 in Brit. Guiana, iii. p. 647). 



" ' This Tortoise has much affinity to P. expansa, WagL, 

 and is distinguished principally by this, that it has only 

 one short beard-thread under the chin. The head is black 

 and shows some white spots ; of these, one is situated behind 



