ON PROTEROSAURUS HUXLEYI. 237 



Proterosaurus Huxleyi, n. sp. (PL VIII.) 



The small specimen of Proterosaurus, though far from being 

 perfect, is not by any means so much mutilated as the large 

 example of the genus above described. It lies apparently on its 

 belly, with the two anterior limbs spread out, and the principal 

 bones of the left posterior limb lying nearly in their natural 

 order, though dislocated. In front of the trunk the neck-joints 

 are scattered about in contact with the right coracoid ; and a 

 little further in advance towards the left is apparently a fragment 

 of the skull, an arched bone five-eighths of an inch in length. 

 The lumbar vertebra? are not present, and the proximal caudal 

 vertebrae are likewise deficient, the slab being broken away at 

 this point ; but a few of the distal ones can be traced. The ribs 

 are spread out on either side of the spinal column, which strongly 

 marks the central line. The trunk of the body from the pelvic 

 region, or from the point where the slab is broken away, to a 

 point level with the supposed cranial fragment, is about five 

 inches in length. 



The bones are in a peculiar state. The surface of most of the 

 limb-bones and ribs is well preserved. These bones seem to 

 have been hollow, and are filled up with galena ; but the verte- 

 brae and some of the smaller bones, such as the carpals, are al- 

 most entirely composed of that mineral ; and when this is the 

 case, the foirni of the bones is often much distorted, apparently 

 by the influence of the lead-ore in assuming its usual cubic form. 



The vertebrae are not in a good state of preservation ; they 

 are much injured by the deposition of the galena, as above re- 

 ferred to, which has so distorted the form of the bones that it is 

 quite impossible to make out the parts, or to say whether or not 

 they are provided with the long characteristic spinous processes 

 of P. Speneri. Indeed, it is difficult to determine the number 

 of joints, though twelve can be counted. As, however, there 

 are fourteen or fifteen pairs of ribs, there must be at least as 

 many dorsal vertebrae. It would still seem, nevertheless, that 

 they are not so numerous in this species as they are in P. Spe- 

 neri, in which we have seen there are seventeen or eighteen 



