12 SYSTEMATIC PALEONTOLOGY 



PrISCODELPHINUS ( ?) CRASSANGULUM n. Sp. 



Plate XI, Figs, la, lb, 2, 3a, 3b. 



Description. — An imperfect skull collected by the Maryland Geologi- 

 cal Survey may belong to this genus. The teeth are all lost but the 

 alveoli seem to indicate that the roots were very slightly flattened, 

 if at all; in the anterior part of the series the alveoli seem to run 

 together and to form an imperfect alveolar groove. If the teeth prove 

 to have the cylindrical roots the form must be considered as a species 

 of Priscodelphinus and only the discovery of vertebrae in connection 

 with the skull can determine whether it is a new species or belongs to 

 one already described. If the roots are found to be more flattened 

 longitudinally it must be considered as a new form near to rliabdosteus 

 but distinguished by the presence of teeth in the whole length of the 

 jaw. 



Eostrum very long and tapering gently, the sides straight. Superior 

 portion of the upper jaw overlapping the lower, so that the alveoli of 

 the teeth are on the inferior side of the angle at the side of the jaw; 

 the upper surface of the jaw formed by the joined maxillaries and pre- 

 maxillaries; the under surface marked by a deep straight groove which 

 corresponds to a similar groove on the superior surface of the upper 

 jaw; the opposed surfaces of the two jaws almost flat. The teeth were 

 not opposed but extended out and forward from the sides of the jaw 

 even in the posterior portion of the series; the teeth were simple and 

 conical in form. The maxillaries did not extend posterior to the orbit, 

 they were greatly expanded posteriorly in thick wing-like extensions 

 that gave the base of the rostrum a considerable width, and passed 

 gradually into the slender portion. Between the posterior portions 

 of the maxillaries the vomer appears very slightly on the inferior sur- 

 face. Above, the vomer is seen to be a rather short V-shaped bone, 

 the posterior ends of which clasp the nodular and very rugose anterior 

 end of the mesethmoid; the cartilaginous extension of this forward 

 was of considerable extent. The premaxillaries were very long and 

 slender, posteriorly they became flattened and thin; from a point just 

 anterior to the nares they diverged as they retreated; anteriorly they 

 were slender and rod-like, anchylosed to the maxillaries but seemingly 



