Tertiary.'] PALAEONTOLOGY OF VICTORIA. [Mammalia. 



are directed backwards, but on one side is confluent with the 

 following vertebra. In the second (immature) example the 

 diapophyses of the fifth (or first caudal) vertebra, coalesce 

 with the fourth sacral on one side, the sixth and seventh 

 (second and third caudal) vertebrae have their diapophyses directed 

 backwards and anchylosed by their extremities. The articulation 

 with the ilium is more extended than in P. latifrons and formed by 

 the first and second sacrals. In a moderately adult specimen 

 before me the four sacral vertebrae are united by the distal ends of 

 their diapophyses and the three following caudal vertebrae have 

 their diapophyses directed backwards without bony union ; but in a 

 very large specimen, otherwise identical, the sacrum by coalescence 

 of the outer ends of the diapophyses by strong bony union includes 

 five vertebrae, the diapophyses of the following caudal vertebrae being 

 directed backwards and not united by bony anchylosis. In several 

 of the specimens the neural spine of the first sacral vertebra is, 

 like our fossil, nearly as high as those of the lumbar vertebrae 

 contrasting with the abruptly lowered or undeveloped neural 

 spines of the following sacral vertebrae, giving the impression that 

 the last lumbar became sacral by anchylosis with the body of 

 the succeeding one and by articulation of its diapophyses with the 

 ilia as Prof. Owen noticed in Phalangista Cooki (see " Comparative 

 Anatomy and Physiology of Vertebrata," vol. 2, page 331). In 

 most of the skeletons before me of P. platyrhinus the third sacral 

 vertebra takes a small part in the articulation with the ilium. 



The os innominatum of the P. platyrhinus differs from P. 

 latifrons in the greater production of the iliac angle, and, according 

 to Prof. Owen, in the narrower and less robust body of the ilium 

 (although I find on comparing two skeletons of P. latifrons and 

 three of P. platyrhinus that the latter is the more robust, so 

 perhaps the character is variable), in the greater length, less width, 

 and less definite bipartition of the articular surface for the sacrum ; 

 in the less prominence of the ilio-pubic process and of the rectus 

 tuberosity ; in the longer and more slender pubis ; in the shorter 

 ridge for the marsupial bone ; in the larger obturator foramen, and 

 the absence of the projection from its ischio-pubic margin ; in the 

 narrower ischium before the expansion of the tuberosity, the less 



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