42 CASE. [VoL. XIV. 
Systematic Relationship of Protostega and Allied Forms. 
The forms most important in this connection are: 
Dermochelyidae. 
Dermochelys Blnv. (35). 
Psephophorus v. Meyer (36). 
Eosphargis Lydekker (30). 
Protostegidae (3). 
Protostega Cope (2). 
Protosphargis Cap. (31). 
(?) Pseudosphargis Dames (28). 
Cheloniidae. 
Osteopygis Cope (37). 
Allopleuron Baur (20). 
Lytoloma Cope (38). 
And also the living forms of the Cheloniidae. 
The known material is deficient in comparable portions, thus 
only a part of a head and nothing of the body is known of 
Pseudosphargis, while the skull is absent and the body very 
perfectly preserved in Pyvotosphargis. Eosphargis is known 
from the skull and very incomplete body skeleton, and so on. 
Conclusions drawn from such material must be, in a sense 
provisional and await the evidence of future discoveries for 
confirmation. 
The Protostegtdae are characterized as a distinct group by the 
presence of descending parietal plates and the absence of a cara- 
pace. In the middle cretaceous form, Protostega, the descending 
parietal plates are well developed. In the upper cretaceous 
form, Protosphargis, as already stated, the skull is unknown, but 
the almost generic identity of the body skeleton with Protostega 
makes the presence of the plates very probable. In Pseudo- 
sphargis of the oligocene they are present, but the lower end 
has only a weak connection with the pterygoid; of this form, 
Dames says (28), p. 17, “ Bei Pseudosphargis endlich bilden sie 
im oberen Theil noch wohlentwickelte Lamellen, die jedoch mit 
ihrem Vorderrande weit hinter der erwahnten Verbindungslinie 
der Orbitae zuriickbleiben, im untern Theile sind sie auf schwache 
Pfeiler reducirt, deren ganzliches Verschwinden eine sphargis- 
