504 DR. J. E. GRAY ON THE GENUS CHELYMYS. [Mar. 19, 



Eagles, I had the use of a very fine series, formed of Mr. Anderson's 

 birds as well as my own. This collection, numbering between 30 and 

 40 birds, is, I believe, the finest there is ; for I have not heard of even 

 Mr. Hume possessing the half-changed striped birds. It was very 

 pretty to see how this striped bird changed gradually into the old 

 black one, and to see, on the other hand, how remarkably distinct 

 A. bifasciata was from A. crassipes in every stage. Beyond the ful- 

 vous on the back of the head the two birds have nothing in common, 

 except that they are of very similar size. 



3. On the Genus Chelymys and its Allies from Australia. 

 By Dr. J. E. Gray, F.R.S. &c. 



[Eeceived February 28, 1872.] 

 (Plates XXVII.-XXIX.) 



Chelymys of Australia, in its more extended sense, forms with 

 Platemys from Tropical America a group differing from all the other 

 Hydraspidce in having a solid skull with a broad square face and 

 crown, with the temporal muscles on the side, and a broad auri- 

 occipital arch. The American genus Platemys is somewhat like the 

 Australian genus Elseya, but differs from it in many particulars 

 sufficiently to shew that it is a distinct genus. 



For many years only a single species, called Emys macquaria by 

 Cuvier, was known ; but as the country has been more searched we 

 have gradually become acquainted with several very distinct species, 

 which in the 'Annals and Magazine of Natural History' for 186/ 

 (vol. xx. p. 44) I separated into two genera, Chelymys and Elseya, 

 the former having no beard on the chin, whilst the latter has two 

 distinct beards, but no nuchal shield. 



In the 'Annals and Magazine of Natural History' for 1871 (viii. 

 p. 117) I separated the genus Euchelymys from the latter because 

 it had a narrow nuchal shield as well as two beards. We have since 

 received from Mr. Krefft several more specimens of these animals — 

 which has induced me to revise the characters of these genera, and 

 also to examine and figure the skulls of two of them, as well as the 

 other parts of the skeleton. I am now in doubt whether the exist- 

 ence of a narrow nuchal plate is a sufficient character for the esta- 

 blishing of a geuus or species ; but I must leave this question to 

 be solved by the discovery and examination of more specimens. As 

 yet we have only a single specimen with a nuchal plate ; and, as far 

 as I have had an opportunity of judging, I think it may probably 

 be an accidental malformation of a comparatively common species 

 without a nuchal plate, of which there are several specimens in the 

 Museum collection. 



The Australian genera have solid, rather thick, skulls, unlike the 



