I02 



and of a regular oval outline. The articular cones are shallow, 

 and have their bottoms but slightly above the centre. The 

 neurapophysial facets are deep, with prominent borders, and 

 the diapophyses are sessile. The chief peculiarity is that the 

 under surface of the centrum has no markings of any kind. 



Measurements. 



M. 



Length of centrum -oio 



Breadth of centrum -040 



Depth of centrum -027 



As Professor Marsh has given no measurements, the ref- 

 erence to A. depressa cannot be certain. 



The specimen was found at Henry's Fork. 



AMIy\ SCUTATA, CopC. 

 Bull, of U. S. Geol. Survey, No. i of Series 11, p 



A species of about the size oi A. ealva, but with a propor- 

 tionately larger head. It is represented in our collection by 

 a specimen which lacks only a portion of the caudal and pec- 

 toral fins. The premaxillary is short and stout, articulates 

 closely with the maxillary, and bears a single row of pointed 

 recurved teeth. These are shorter and straighter than in A. 

 calva. The maxillary is much as in the modern species, but is 

 rounder. The cranio-facial axis is straight and broad ; the 

 basiocciptal is the largest of the bones ; the basisphenoid and 

 prespJicnoid are of the usual shape and size, but there is a 

 constriction at their junction which is not marked in the 

 modern species. The vomer is long and double, and at the 

 extremity is armed with rows of small teeth. The two por- 

 tions diverge more perceptibly than in A. calva, and are 

 stouter, though this appearance may, to some extent, be due 

 to flattening. 



Th.Q frontal is long, broad, and thick ; the upper surface is 

 delicately sculptured in a somewhat different pattern from 

 that seen in the modern species. The parietal is short and 

 broad, while the epiotic is unusually narrow. The mandible is 

 long and slender ; the rami are incurved anteriorly, but ap- 

 parently not to the same extent as in A. calva. The articular 



