Nov.2i,i895. SKELETON OF Protostega gigas HAY. 61 



times this length, and we might therefore infer that the shortest cer- 

 vical would have a length of about no mm. The longest vertebra in 

 his possession was only 60 mm. long and had at least one plane sur- 

 face. It is quite improbable therefore that it belonged to the ani- 

 mal's neck. The longest neck vertebra, the last but one, of a speci- 

 men as large as the one described by Professor Cope should have a 

 length of about 142 mm., and the longest dorsal vertebra, the third, 

 should have a length of near 270 mm. Professor Cope's account of 

 the longest vertebra in his possesion makes it not improbable that it 

 was the first sacral. The other vertebrae almost certainly belonged to 

 the tail. Their size and the form of their articular surfaces both 

 support this interpretation. 



Ten ribs were in Professor Cope's hands. Each had a proximal 

 expansion, and it was evident that these ribs did not unite suturally so 

 as to form a carapace. But since the dorsal vertebras were regarded 

 as being so small, the conclusion was reached that either the expanded 

 proximal ends interfered with each other in the middle line or the 

 ribs must have been articulated to diapophyses. Since, however, the 

 dorsal vertebrae would have varied in length from 1 08 to 275 mm., 

 and would have been proportionally wide, while the widest rib de- 

 scribed is 140 mm. at the proximal end, there is no necessity for be- 

 lieving that any rib touched either its fellow or its neighbors. The 

 second, third, fourth, and fifth vertebras probably ranged from 250 

 to 275 mm., and the next two or three were not much shorter. In 

 Dermochelys and Protosphargis the ribs in front of the fifth from the 

 last are little, if any, broader than this fifth. Hence we may safely 

 conclude that there were wide spaces between the ribs even near the 

 vertebral column. The ribs certainly lacked little of having reached 

 as advanced a stage of reduction as they have in Dermoehelys. Their 

 condition was probably much like that seen in Capellini's restoration 

 of Protosphargis. 



Professor Cope estimated that the head of the individual which he 

 described had a length of 24^6 inches. However, basing my estimate 

 on the length of the maxillary bone as figured on plate X of "Cretace- 

 ous Vertebrata," and making the ratio of this maxillary to the length 

 of the skull the same as that found in Thalassochelys, I can make the 

 whole length of the skull, including the supraoccipital spine, only 

 about 1 8 inches, or 45 cm. The distance from the snout to the con- 

 dyle would be close to 13 inches, or 32 cm. Professor Cope's specimen, 

 judging from the size of the plastral bones in his possession, was not 

 much smaller than my own. Hence if we estimate at 32 cm the head, 

 measured to the condyle, we shall probably not make it too great. 



