G. P. Wieland — On Marine Turtles. 105 



Kansas chalk. Owing to this freedom from crushing, it has 

 been possible to restore with approximate accuracy the outline 

 of the skull, carapace, and plastron, although all the elements 

 of the entire skeleton were dissociated during erosion from 

 their matrix, those recovered being as follows : 



Skull, with lower jaw, — nearly complete, one squamosal and 

 certain minor portions only missing. 



Carapace: Nuchal; first .to fourth neuralia ; pygal ; fairly 

 complete series of ribs ; first and second marginalia of both 

 sides, with third and fourth of right side. 



Plastron : Alae of the entoplastron ; hyoplastron of right 

 side ; hypoplastic and xiphiplastra complete. 



Shoulder girdle : Both humeri and the procoraco-scapulars, 

 with coracoid of right side only. 



Pelvis : Only the right ischium missing. 



The chief parts lacking, therefore, are the radius and ulna, 

 the femora, and the bones of the hands and feet. 



The dissociated elements of the cranium, as brought together 

 and mounted with the lower jaw, afford the most satisfactory 

 representation of a Protostegan skull thus far seen. In fact, 

 the result displayed by photographic figure 1 must be of 

 nearly the true form, since in addition to the presence of the 

 lower jaw and nearly all the exterior elements, the main 

 outline is further confirmed by the practically complete pala- 

 tines, pterygoids, and quadrates. Only in the interior of the 

 skull are clear characters lacking; for instance, the descending 

 process of the parietals, noted by Dr. Hay in Protostega 

 advena, cannot be observed. 



In the main, the present fine cranium merely serves to 

 corroborate the characters of the Protostegan skull, as already 

 determined, and to bring out more clearly the major differences 

 from Archelon. Thus, the strongly decurved beak and the 

 upturned nares of the latter genus are absent, the outlines 

 being more like those of other sea-turtles, with the orbits fairly 

 well forward. The low-set squamosal, which certainly sent up 

 a process along the posterior border to meet the parietal, how- 

 ever, is a family characteristic. The general outline reminds 

 one not a little of the skull of Colpochelys Kempii Garman. 

 Interiorly, there is no great conelike palatal projection of the 

 vomer, as seen in Archelon. 



While the present species is here defined as new, there is no 

 very marked character not possessed by Protostega gig as, spe- 

 cific differences being mainly exhibited by the smaller limbs 

 and the heavier carapace and plastron now to be described. 



Carajyace. — Hitherto it has not been possible to gain a 

 satisfactory picture of the shell of any species of Protostega. 

 All the specimens known have either lacked a large part of the 



