Cope.] 432 [March 1, 
exhibit no indications of contact. ‘The length of 7.8 feet, for the cara- 
pace is not then too much, and estimating from the size of the head is 
too little. We can then safely conclude that the carapace of this turtle 
is more elongate and narrowed than existing forms. Thus in Chelone 
mydas the carapace is six-eighths as wide as long. 
It remains to discuss the question of the age of the specimen. It 
might be objected that the absence of carapace, and the radiate character 
of the margins of many of the bones indicate that our type specimen is 
young. To this it may be replied (1), that it is in the (?) sternal bones 
unlike the young of any known type, when certain of their bodies do at 
all times exhibit smooth margins as boundaries of the points of exit of 
the limbs; moreover, it is possible that these plates were dorsal. (2) 
The superior or inner extension of the marginals exceed that of any 
known tortoise in the adult condition. (8) The articular bone is ossified. 
(4) Separate ribs should be discovered among extinct tortoises as an 
adult character, on theoretical grounds, the more as it exists in one re- 
cent genus (Sphargis, vide Wagler). 
Afinities. In discussing these, one point heretofore left doubtful may 
be first considered. The large flat elements described as lateral dermal 
bones ; are they ossifications of the dorsal or ventral integument? They 
were found below all the other bones, and nearly all the ribs laid on them 
with their heads turned upwards. This rendered it probable that the 
shields were dorsal, and that the animal was entombed on its back, and 
a coracoid, which was afterwards found lying immediately on the largest 
bone (No. 10), crossed in its course parts of two ribs. This could not 
have been the case had the shields been ventral. An examination of the 
shields does not reveal any conformity to any known type of Testudinate 
plastron. The bones radiate in all directions, leaving no margins for fore 
and hind limbs, or for a median fontanelle, still less for suture with each 
other. 
Should these bones then be regarded as dorsal, they constitute a char- 
acter not previously noticed in the order, but one whose homologue is 
seen probably in the dermal shield of bony tesselated plates seen in 
Sphargis. The other points of affinity to Sphargis are the distinct ribs ; 
the thin laminiform jaws with cutting edges; the quadrate bone with 
such a strong anterior concavity ; the elevated position of the zygomatic 
bone ; the form of the humerus. Points of special resemblance to Chelone 
are: the short posterior superior portion of the quadrate ; the entire 
edge of the maxillary bone ; the deep dentary. The points in which it 
differs from both, are numerous. They are: the dorsal shields, the mar- 
ginals, the notched symphysis, etc. ; the shortened articular end of 
scapula ; the elongate form of the carapace, ete. 
The constant separation of the ribs, and the short vertebra, are char- 
acters which are more like those possessed by other reptiles, than those 
characteristic of Testudinata. The presence of dermal dorsal bones is 
of the same kind. The genus Protostega then belongs near the Spharg- 
idid@ in the suborder Athecw, and is in some points to be approximated 
to the Chelonidida. 
