MARYLAND GEOLOGICAL SURVEY 53 



oblique to that of the section, and parallel to that of the superior 

 oblique part of the external face. It is shallower than in the Ulius 

 moratus, and the species of Cetotherium, and is separated by a wide 

 osseous space from the inferior border. That this form is descended 

 from one with a larger canal is indicated by the fact that the fractures 

 of the ramus display a closed fissure extending from the floor of the 

 canal vertically downwards. The canal is overhung on the inner side 

 by a narrow free border of the superior perforate wall. 



Measurements. 



m. 



Length of fragment 607 



( vertical 077 



Diameters posteriorly | ^^^^^^^^^^ ^^^ 



vertical 070 



Diameters more anteriorly ■ , ^^^ 



transverse 065 



r^. , -,. , f vertical 073 



Diameters near distal extremity \ 



transverse 056 



" For a length of 200 mm. from the anterior extremity the borders 

 of the gingivodental groove are sufficiently well preserved to demon- 

 strate that it was not closed. The edges posterior to this are more or 

 less worn, so that the roof might be supposed to have been broken away 

 in the absence of other evidence. This is, however, forthcoming, for the 

 internal border is so far preserved near the posterior extremity for a 

 space of 135 mm. as to show that no roof has existed. 



" Omitting consideration of the generic characters, the following 

 comparisons with other species may be made. In the Ulias moratus 

 the gingivodental groove is deeper and narrower, and the inner edge 

 is much narrower. The external face is not so convex. The Siphono- 

 cetus priscus of Leidy resembles it more nearly in form, but the superior 

 (external) foramina are not so far inwards, and the two canals taken 

 together conform nearly to the outline of the ramus in section, which 

 is far from being the case in the TretuUas huccatus. There is no 

 Meckelian groove. In the Cetotherium palceatlanticum Leidy, the ex- 

 ternal face is not so convex, and the internal gingival canals are. 



