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a deep vertical groove behind ; it has also a moderately well-developed spinous process : the 

 eighth vertebra has the centrum convex at both ends and much compressed in the middle. 

 The posterior sygapophyse* of the eighth cervical vertebra form a wedge-shaped process, 

 which enter* a cleft formed by the anterior lygapophyses of the first dorsal. 



The first dorsal vertebra has short thick depressed ribs, united as usual by suture to the 

 costal plates connate with the succeeding ribs ; these are articulated by suture partly to their 

 own centrum, and partly to that of the first dorsal vertebra. The expanded costal plates of 

 the second pair of ribs present deep oblong cavities for the reception of the anterior inflected 

 angWs) of the hyostemals, to which they are firmly joined by strong suture. The neural arch 

 of the second dorsal is also advanced so as to rest partly upon the centrum of the first , the 

 expanded median dermal plate of the carapace, which is confluent with the compressed neural 

 spine of the second dorsal vertebra, also rests, but without coalescing, upon the neural spine 

 of the first dorsal vertebra. The centrums of the seven succeeding dorsal vertebrae are as 

 remarkably expanded laterally and depressed as those of the neck are compressed. The 

 fourth pair of costal plates, connate with the ribs of the fifth dorsal vertebra, articulate with 

 the hrposternals by oblong excavated sutural surfaces, like those on the second costal plates. 

 Two rough subtriangular surfaces are slightly excavated in the expanded plates connate with 

 the ribs of the eighth and ninth dorsal vertebrae, to which the expanded summits of the iliac 

 bones are firmly united. Short pleurapophyscs from the two succeeding vertebrae abut 

 against the inner sides of these excavations, and indicate the segment analogous to a sacrum. 

 Three vertebrae succeed these, and terminate the series in this skeleton. 



The parts of the plastron, the scapular and pelvic arches, and the bones of the extremities, 

 are described in the volume of the ' Ossemens Fossiles ' above cited. 



Presented by Sir Everard Home, Bart., F.R.S. 



Genus Hydrtupu. 



961. The skeleton of the long-necked freshwater Tortoise of Australia (Jfydraiyns 

 longicoUu, Bell ; Chelodina, Fitzinger), with a portion of one side of the cara- 

 pace removed. 



The head is much depressed ; the mastoids are excavated by large tympanic cells, and pro- 

 longed backwards ; the frontal is produced forwards as far as the anterior nostril, where it 

 terminates in a point between the two nasals, which are here distinct from the prefrontals. 

 The margins of the upper and lower jaws are trenchant : the hypapophysis of the atlas has 

 the form of a diminutive wedge-bone, forming as usual the lower part of the articular cup for 

 the occipital condyle : the rest of the body of the atlas, or ' odontoid,' has coalesced with its 

 proper neural arch, which developes two transverse and two long posterior oblique processes, 

 as in the Ckrlyt. The second, third and fourth cervical vertebrae have the fore part of the 

 centrum convex, the hind part concave : the fifth centrum is biconvex : the sixth is concave 

 in front and convex behind : the seventh is biconcave : the eighth is biconvex. The poste- 

 rior lygapophyses in this vertebra are blended together, and form a single semicy lindrical 



2 n2 



