184 G. R. Wieland — Upper Cretaceous Turtles. 



It is thus seen that the cranial characters of Lytoloma 

 angusta Cope are inferentially known and point conclusively 

 to a position in the Cheloninee, although as yet no adequate 

 description of a Lytoloman carapace from the Greensand of 

 New Jersey has been given. It is therefore of distinct interest 

 to find that the Yale specimen No. 625 proves to be a fairly 

 complete carapace, with marginals so distinctly like those of 

 L. angusta as to indicate their specific identity. Moreover, the 

 rather close relationship to Tropleura, and the various primi- 

 tive characters present, add to our knowledge of the early 

 marine forms, and bring us a step nearer to the actual lines of 

 descent of existing marine turtles from littoral forms. While 

 not known to have survived beyond the Eocene, the Lytolomas 

 show by their structure that they were not more than generic- 

 ally removed from the existing genus Chelone. Before passing 

 on to the description of the carapace, however, it will, because of 

 the extended synonymy just reviewed, the considerable number 

 of years since the collection of the materials from New Jersey, 

 and the fragmentary condition of many of the specimens, 

 be necessary to note briefly the evidence as to accompanying 

 cranial characters. 



as. 



Figure 1. — Lytoloma angusta Cope. 



d m 



Superior and lateral view of Denta- 



lmm. xf. (Y. S. 913, from Upper Cretaceous Greensand of Hornerstown, 

 New Jersey, c. s., coronoid suture and sutural surface; s, splenial suture 

 and sutural surface ; d, dental foramen (orifice slightly arched over) ; /, nutri- 

 tion foramen (for mandibular branch of jugular vein — Bojanus) ; m, masse- 

 teric fossa (insertion of masseter muscle). 



The Tower Jaw. 

 Evidence of the specific association of lower jaws and mar- 

 ginals of the Tytoloma angusta form is not abundant in the 

 Yale collections, though fairly conclusive. A dentalium which 

 is accompanied by a fragmentary but characteristic marginal is 



