SKULL OF THE TORTOISE. 131 



the acromion, bends inwards to meet its fellow at the 

 middle line. The coracoid continues distinct from the 

 scapula, expands, and becomes flattened at its median 

 extremity, which does not meet its fellow or articulate 

 with the sternum. The iliac bones, 62, are vertical and 

 columnar, like the scapula, but are shorter and more com- 

 pressed : they articulate, but do not coalesce, with the 

 pubis, 64, and ischium, 63. The acetabulum is formed 

 by contiguous parts of all the three bones. The pubis 

 arches inwards, and expands to join its fellow at the me- 

 dian sj^mphysis and the ischium posteriorly. It sends 

 outwards and downwards a long, thick, obtuse process from 

 its anterior margin. The ischia, in like manner, expand 

 where they unite together to prolong the symphysis back- 

 wards. 



In the skull, the parietal crista is continued into the 

 occipital one without being extended over the temporal 

 fossae, as in the turtle; the fascia covering the muscular 

 masses in these fossae undergoing no ossification. The 

 bony hoop for the membrana tympani is incomplete 

 behind, and the columelliform stapes passes through a 

 notch instead of a foramen to attain the tympanic mem- 

 brane. The mastoid is excavated to form a tympanic air- 

 cell. In the Australian long-necked terrapene Qiydraspis 

 hngicollis) the head is much depressed, the mastoids are 

 excavated by large tympanic cells, and prolonged back- 

 wards: the frontal is produced forwards as far as the an- 

 terior 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 arti- 

 cular cup for the occipital condyle: the rest of the body 



