195 



it is a rough, prominent, muscular insertion. The l)one extends in a loiiij 

 sword-shaped process, on the inside of the ramus, to l)eyond its middle; 

 externally, it is soon covered by the thin truncate edge of" the dentary. This 

 element is very large. From the angular it rises steeply to a coronoid process, 

 which lias a slight outwardly-twisted eminence, and then follows a gently 

 concave line to the symphysis. The teeth are as follows : Two large — a 

 transverse groove ; tliree large; four very small; nine medium; and two very 

 small — total, twenty. These teeth have straight cylindric-conic crowns, with 

 cementinn without stri^ or facets. The larger are a litllc ((impressed. 



Measurements of the jaws ciud teeth. 



M. 



Length of the premaxillary boue ou the alveolar border 0. 04.') 



Di^pth of the premaxillary bono on the alveolar border 0. 09:J 



Thiclciiess ou the alveolar margin 0. 01(> 



Length of the crown of the second tooth 0. ()4i) 



Diameter of the crown of the same at the base 0. 014 



Length of the maxilhiry bone from the premaxillary 0.270 



Depth of the maxillary bone at the condyle 0. OSO 



Depth of the maxillary bone at the middle 0. 046 



Length of the crown of the third large tooth 0. 028 



Diameter of the crown at the base 0.011 



Length of the crown at the second .small tooth from the large 0. 006 



Diameter of the crown at the base 0.004 



Length of the ramus mandibuli 0.350 



Length of the angle 0.040 



Length of the angular bone exteriorly 0. 080 



Depth at the coronoid process 0. 112 



Depth at the fourth tooth 0.080 



Length of the crown of the first tooth 0. 038 



Diameter of the crown at the base 0.011 



Length of the crown of the fourth tooth 0. 055 



Diameter of the crown at the base 0. 016 



The opercular bones are thin ; the operculum broad ; the preoperculum 

 rather narrow. The latter is without armature, and has some shallow 

 grooves radiating toward the circumference. Length of bone vertically, 

 0'".245 ; radius from inner curve, 0"'.09. 



Tiie vertebrce display deep lateral grooves ; articular faces smooth. Length 

 of centrum, 0'".028 ; diameter, O^.OrtS. The fan-shaped ha3mal spine, or 

 second of the caudal fin, is like that of P. thauinns, but smaller. The last 

 caudals contract in size very rapidly ; the cup of the penultimate, or last, is 

 transverse diamond-shaped. 



The fragments of the saber-shaped veuiral apine display several layers of 

 parallel striate dense bone; and the edge is tubercularly dentate, and one side 

 is much more rugose than the other. At the base, one side is (lat, the other 

 convex ; and there is a transversely rugo.se band near one edge. 



