1895.] 14:d [Cope. 



superior edge becomes proportionally narrower, and at the extremity of 

 the ramus is about as wide as the internal superior ridge. The extrem- 

 ity of the ramus is, in profile, truncated obliquely backwards and down- 

 wards to the obtuse angle at which it meets the slight rise in the outline of 

 the inferior margin. The external plane is slightly concave. The internal 

 face exhibits two surfaces, a superior convex portion which widens down- 

 wards and backwards, and an inferior wider flat portion separated from 

 the superior by a straight ledge. The inferior border of the ramus is rep- 

 resented by an angle of about 70° for the greater part of the length. Below 

 the region where the alveolar borders are equal the angle is more nearly 

 right owing to the increased convexity of the external face. It is rounded 

 below the coronoid process (which is broken off) and widens towards the 

 angle. It is rounded on the distal third, becoming narrower rapidly 

 towards the distal extremity. 



Measureinents. 



M. 



Length of ramus restored ; on curve 1.900 



Length of proximal fragment 790 



Length of distal fragment 390 



Transverse diameter near condyle 070 



Transverse diameter where alveolar borders are equal 060 



Transverse diameter at distal end of long fragment 057 



Vertical diameter where alveolar edges are equal 073 



Vertical diameter at distal end of long fragment 074 



Vertical diameter at proximal end of distal fragment 079 



Transverse diameter at proximal end of distal fragment. . . .049 

 Vertical diameter of extremity 085 



Besides the generic characters, the V lias mora tus presents various spe- 

 cific difl"erence3 from the various species of Balaenidae which are known. 

 The flatness of the internal face and the lack of decurvature distin- 

 guishes it from several of them ; and the absence of fissure at the distal 

 mental foramen separates it from others. I know of no species which 

 has only one series of foramina and that one on the median line, on the 

 distal fourth, except the present one. The size of the ramus resembles 

 that of the CetotJierium palceatlantieum of Leidy, and represents a species 

 of about twenty -five feet in length. 



Tretulias buccatus, gen. et sp. nov. Plate vi. Fig. 3. 



Char. gen. — Dental canal obliterated, and dental groove without osseous 

 roof. Gingival canals and foramina present at one side of the alveolar 

 groove. 



The presence of the gingival canals and foramina in this genus, and 

 their absence in Ulias, suggests two alternative phylogenies. First, it is 

 possible that Tretulias is derived from Siphouonetus by failure of the roof 

 of the gingival groove to develop external to the gingival canals by re- 



