191 



uals, which inchide large portions of the cranium, two almost entirely com- 

 plete. Others embrace jaws, and one a large part of the vertebral column, 

 with segmented caudal rays. In one, these rays were found with the cutting 

 pectoral ray above described, while the simple flat ventral rays occur with 

 ceveral specimens. In none have any traces of symmetrical spinous rays 

 been found, nor strong interneurals capable of supporting such. In none of 

 the more perfect specimens with crania have the segmented rays been found; 

 but the fossil of P. thaumas, where they occur, is represented by a vertebral 

 column and its appendages, which do not differ appreciably from those of P. 

 molossus. 



In the cranium of this genus, there is a well-marked supraorbital rim. 

 Each opisthotic forms a prominent angle, directed posteriorly on each side of 

 the exoccipital. The parasphenoid is a stout and narrow bone, deeply emar- 

 ginate behind for the passage of the muscular canal. It has a transverse 

 expansion in front of the base of the prootic, which rests on a backward con- 

 tinuation of the same. Tliis expansion is pierced behind by two round fora- 

 mina. The shaft is abruptly contracted in front of the expansion, and is tri- 

 gonal in section. The prefrontal extends downward and forward, and carries 

 inferior and anterior articular faces for the maxillary; the latter vertically 

 transverse. The postero-inferior portion of the ethmoid bears on its posterior 

 extremity a concave articular face, which opposes that of the vomer. The 

 floor of the brain-case in front of the prootics is supported by a vertical style, 

 which is bifurcate above, and rests on the parasphenoid below. 



There are large thin supernumerary bones attached to the upper side 

 of the distal half of the maxillary, as in various clupeoid genera. There is a 

 chain of thin suborbital bones. The crest of the vertex /is compressed, and, 

 in one, at least, of the species, greatly elevated and overlapped by a super- 

 ficial thin bone, wiiich forms a laminar extension of the crest in front of it. 

 There is neither enamel nor sculpture on the cranium in any of the known 

 sj^ecies. 



Of the teeth in general, it may be added that their pulji-cavity is rather 

 large at the base but rapidly diminishes in the crown. The mode of succes- 

 sion is by direct displacement from below. The young crown rises into the 

 pulp-cavity, and destroys the vitality of the crown wliile tlic root is absorbed 



