No. 1.] RELATIONSHIPS OF PROTOSTEGA. 47 
ing to the pterygoids in front of the supraoccipital and the 
prootics, it differs from that of all other Chelonzans. Thus, in 
addition to the shape of the humerus and the proportions of 
the phalanges, the fore limb differs in the radius and ulna being 
subequal in length and placed side by side in a horizontal 
plane, and in the fifth metacarpal, instead of the first, being 
the shortest.” . 
In 1889 appeared Baur’s reply to these papers (23). Taking 
up Dollo’s objections first, he stated the belief that the fonta- 
nelles in the carapace of Dermochelys might be filled up by the 
expansion of the elements of the dermal carapace, after they 
had lost connection with the inner skeleton, citing as an exam- 
ple of such disappearance of the fontanelles the case of an old 
specimen of Aspizdonectes (Amyda) muticus. 
He showed that the oldest known specimen of turtles was 
not Zhalassemys Riitimeyer, with fontanelles, but Progano- 
chelys Quenstedtit Baur, which had no fontanelles; also, that in 
some of the living sea turtles the carapace becomes closed in 
old age (Colpochelys and Thalassochelys). He showed that the 
direct ancestors of the sea turtles had no fontanelles in the 
carapace, and that the plastron was stronger than in recent 
forms. To the objection that the embryonic forms showed 
fontanelles in the carapace he replied that the principles of 
embryology could not be used in interpreting the meaning of 
the ontogenetic development of dermal ossifications. 
He applied the statement that the ontogenetic development 
of the exoskeleton was of slight morphological value to the 
statement by Dollo that if Baur’s hypothesis was a true one, the 
embryo should show simple ribs becoming confluent, and again 
single, and also to the objection that the dermal ossifications 
overlay the plastral elements from which they were supposed 
to take origin. 
He showed that the posterior nares were the same in Dermo- 
chelys as in the Chelonizdae, that the nature of the articular 
faces of the cervical vertebrae was constant, and that the plas- 
tron of Dermochelys was reduced from a stronger form. He 
reéstablished his series based on the claws as follows: “Bei 
Caretta (Eretmochelys) sind gewohnlich 2 Klauen vorhanden 
