146 MAURICE G. MEHL 



the mandible. This irregularity of size and spacing of the alveoli 

 is probably largely due to the different ages of the teeth; that is, 

 to loss and replacement of some. Well-developed, rounded ridges, 

 such as are seen on the ventral surface of the rostrum, are present 

 just within the Knes of alveoH. In this specimen they are promi- 

 nent anteriorly, combining near the anterior end and gradually 

 spreading posteriorly. They become less prominent toward the 

 posterior end of the symphysis and are entirely wanting before this 

 point is reached. 



The second specimen referred to in the preliminary notice of 

 Angistorhinus grandis^ would, it was hoped, when worked up, fur- 

 nish a complete skeleton of that form. It was found, however, 

 that the matrix was a hard, extremely tough sandstone and almost 

 impossible to free from the bone, as the latter was in every case 

 found to be softer than the matrix and extremely brittle. For these 

 reasons a further attempt to prepare a skeleton has been abandoned, 

 for the present at least. Aside from the skull, a portion of the 

 posterior border of which is missing, and the lower mandible, which 

 also lacks a little of the posterior extremities, only a single dorsal 

 vertebra, several abdominal ribs, and quite an assortment of un- 

 associated teeth are available for description. These serve well, 

 however, to set the specimen off as a species distinct from A. 



grandis. 



Angistorhinus gracilis Sp. Nov. 



This skull, which I take to be that of an adult individual, prob- 

 ably had a length of about 985 mm., somewhat greater than that 

 of the specimen of A. grandis. The greatest length preserved, 

 which does not quite include the quadrate, is 920 mm. This is 

 somewhat greater than the same measurement of A. grandis, but 

 in spite of this the latter is the more massively built skull, a point 

 that is especially noticeable in the form of the mandible to be 

 discussed farther on. 



OPENINGS OF THE SKULL 



The supratemporal fenestrae are missing, but from the close 

 resemblance of the skull to A . grandis in other respects these open- 



^ Jour. Geol., XXI (1913), 190. 



