20 



\ 1 ' 1 ' 1 N I > 1 X TO Till'. r\T\!.<>i;l !•: UK S1I1KL1) KKITILKS. 



and description of the oarapaoe Lead me to believe thai LI 

 ix most closely allied to Borne of oui existing Bpeoiea of the 

 trioted genua Hydraspis, which has only been hitherto 

 found in Tropioal America. It is peculiar among the species 

 of that genus tor the laxj the Lntergular plate, tho 



small triangular gular plate and for the small si/.o and 

 triangular form of the postgular. Tho pectoral plates, on 

 the contrary, are longer than the abdominal plates; tho 

 underside o( the marginal plates opposite the suture, 

 between the pectoral and abdominal plates, being rather 

 broader than the rest, and angular on the inner edge, which 



I have U0< seen in any recent species. (Ann. & Mag. Nat. 



II -• L871, vol. viii. p. 'MO.) 



PLATEMYS (p. 75), add :— 



Skull: basisphenoid short, very broad, angularly pro- 

 d between the palatines in front; basioecipital short, 

 transverse, nearly as broad in front as tho basisphenoid, 

 and contracted behind. (Wagler, Amph. tab. 4. f. 7.) 



The Australian genera of this section have solid, rather 

 thick skulls, unlike the thinner skulls of the American 

 genus Platemys. They may be divided thus : — 



I. Head covered with a skin, which is reticulated over the 



the temples; nuchal plate distinct; neck smooth, 

 reticulated. 



1 . Ckeltmys. Chin not bearded ; nuchal plate generally 



broad; occiput like the crown. 



2. ErcHELTJirs. Chin two-bearded ; nuchal plate nar- 



rower ; sides of occiput with two oblong, subtrian- 

 gular, diverging, hard plates. 



II. Head and temporal muscles covered with a hard, bony 



sheath ; nape spinose ; chin two-bearded ; nuchal 



plate none (or, rarely, very small and narrow). 



3. Elseta. 



For many years only a single species, called Emys mac- 

 quaria 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,' 1867, vol. xx. p. 44, I sepa- 

 rated 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,' 1871, vol. viii. p. 117, 

 I separated the genus Euchehjmys from the latter because 

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

 have since received from Mr. Krefft several more speci- 



mens of these animals— which has induced me to revise the 

 characters of those genera, and also to examine and figure 

 the skulls of two of them, as well as the other parts of the 

 skeleton. 1 am now in doubt whether the existence of a 

 narrow nuchal plate is a sufficient character for the esta- 

 blishing of a genus or species ; but I must leave this ques- 

 tion to be solved by tho discovery and examination of more 

 specimens. As yet we have only a single specimen with a 

 nuchal plate ; and, as far as I havo had an opportunity of 

 judging, 1 think it may probably be an accidental malfor- 

 mation of a comparatively common species without a nu- 

 chal plate, of which there are several specimens in the 

 Museum collection. 



CHELYMYS (p. 75), add :— 



Head covered with a smooth skin, reticulated and divided 

 into small plates over the temples. Chin slightly, very ob- 

 scurely bearded. Nape smooth, reticulated. Legs covered 

 with small scales. Nuchal shield broad and well developed. 

 Crown and occiput nearly square, scarcely dilated behind ; 

 hinder edge produced in the middle. 



Vertebral shields of the adult quite as long as broad. 



Skull depressed, without any zygomatic arch, and with a 

 large tympanic opening ; forehead and erown broad, flat, 

 produced behind in the middle of the occiput. Basisphenoid 

 transverse, short and broad, with a triangular projection 

 on the front edge, produced behind the hinder part of the 

 palatine bones. The basioecipital oblong, transverse, as 

 broad as the sphenoid. — Gray, P. Z. S. 1872, p. , fig. 



I am inclined to think that more than one species were 

 included under the name of Chelymys macquaria in the 

 Catalogue and Supplement, some even belonging to what 

 is now regarded as another genus, as they have two beards, 

 which were overlooked in the stuffed specimens. 



* Thorax ovate, more or less depressed, with the hinder 



margin expanded. Head of moderate size. 

 * 



1. Chelymys macquaria (p. 75), substitute ; — 



Emys macquaria, Cuvier, R. A. vol. ii. p. 11. 

 Hydraspis macquaria, Gray, Synopsis Kept. p. 40. 

 Emydura macquaria, Bonaparte, Tab. Analyt. p. 8. 

 Platemys macquaria, Dumeril <J" Bibron, Erpetol. Generate, 



Sf Cat. Meth. p. 21. 

 Chelymys macquaria, var. 1, Gray, Cat. Sh. Rept. p. 57 ; 



P. Z. S. 1872, p. 

 Hydraspis australis, Gray, in Gray's Travels in Western 



Australia, vol. ii. p. 445, tab. vi. 



Ilab. Australia, Macquarie River (Gould, 1840). 



