5.t4 on the systematic position of miolania. [June 23, 



10. On the Systematic Position of the Genus Miolania, Owen 

 {Ceratochehjs, HuxiejO. By G. A. Boulenger, F.Z.S. 



[Keceived June 10, 1887.] 



Tlie remains of the large Australian Quaternary Reptile Mio- 

 lania, recently referred by Prof. Huxley ' to the order Chelonia, have 

 at the same time been rej^arded as indicating an animal closely allied to 

 the recent genera Chelydra, Macrodemmysi^Giipochelys), and Plafy- 

 sternum—K fact which would be of great interest, since the group 

 Cryptodira, to which those genera belong, is, at the present day, 

 unrepresented in the fauna of Australia. 



By the kindness of Dr. Woodward I have been able to examine 

 additional material, among which is a nearly perfect skull with the two 

 first cervical vertebrae attached, which was in the hands of Sir R. 

 Owen at the time Prof. Huxley wrote his note. And I have come 

 to the conclusion that, far from bearing any affinity to the Cheli/dridx 

 or Fluty sternidce, the extinct Chelonian belongs, like the recent 

 forms of the Australian region, to the group Pleurodira. The 

 structure of the alveolar surface of the skull indicates beyond doubt 

 an herbivorous animal; the ungual phalanges and the curious sheathed 

 tail, I should say, a terrestrial one. The different hahits would, 

 tlierefore, account for some discrepancies on comparison with the recent 

 representatives of the Pleurodira". The structure of the tail, with its 

 opisthocoelous centra, is unique among the Pleurodira and points to 

 a distinct family {Miolaniidce). The pelvis also must have differed 

 from that of existing Pleurodira, the ilium showing a surface for 

 attachment to a sacral rib. 



The principal characters which induce me to refer Miolania to 

 the group Pleurodira are the following : — 



1. The pterygoids are very broad, not narrowed posteriorly ; their 

 outer palatal borders, instead of being emarginate, form wing-like 

 expansions. 



2. The tympanic cavity is completely surrounded by the bony 

 " roof," whilst in all known Cryptodira, however great the develop- 

 ment of the roof, the tympanic disk is free behind. 



3. The mandible articulates with the skull by a condyle fitting 

 into an articular concavity of the quadrate — a character by which 

 the Pleurodiran Chelonians differ from all other Reptilia, so far as I 

 am aware. 



4. The cervical vertebrae are those of a Pleurodiran ; a strong and 

 long transverse process is present, and the posterior bordeis of the 



1 Proc. Eoy. Soc. xlii. p. 232. 



- All recent Pleurodira are thorouglily aquatic, and, ■with the exception of 

 rodocncmis, carnivorous. The singular canal leading to (lie orbit, formed by 

 the curved-up anterior wings of the pterygoids, as well as the lateral eliambers 

 of the shell, are secondary characters in correlation wifli tlie diving powei-s, and 

 occur also, more or less developed, in some of the most flioroiiyhly aquatic 

 Cryptodira, e.g. Bafagpr anA rtychcim/a. See Riitiujcyer's remarks, A'crli. nat. 

 Ges. Basel, vi. 1S74, p. .58. 



