185 



at the base of which are one or more foramina. The postfrontal shares with 

 the pterotic the support of the hyomandibular. The prootic is elongate, and 

 sends a crest downward and forward to the basis of the above-mentioned 

 process of the parasphenoid. Superiorly, it bounds, with the pterotic and 

 sometimes (Portheus) opisthotic, a large foramen. 



The premaxillary bones are short, and form but a small portion of the 

 upper jaw. The maxillary is elongate and simple. The hyomandibular is 

 rather narrow, and does not present an elongate support for the operculum. 

 The symplectic is well developed, entering far into the inferior quadrate. The 

 latter is a broad bone, large, in contact with the metapterygoid, which is 

 itself a thin plate, nearly attaining the pterotic. In Portheus, the pterygoid 

 is well developed as a broad plate extending to the inferior boundary of the 

 orbits. The palatine Exhibits a marked peculiarity in the genera of this fam- 

 ily. It is a shortish bone, soon uniting postero-inferiorly with the ectoptery- 

 goid, but supporting as its supero-anterior extremity a body comparable to 

 the head of a hammer. This malleolar body, as it may be called, is a short- 

 ened cylinder, with one extremity articulated to the prefrontal and the other 

 to the posterior superior of the maxillary facets. This gives the latter bone 

 a firmness of support unusual among fishes. It also probably permits 

 of some movement of the maxillary in a horizontal plane, which, though 

 small, would have the effect of considerably expanding the gape of the 

 mouth, thus enabling these fishes to swallow large bodies, in the maimer 

 of the Mosasauroids of the same sea and epoch. 



The ectopterygoid is a large bone, and extends down on the front of the 

 inferior quadrate Neither it nor the palatine supports teeth in any of the 

 known genera. 



The sclerotica of the eye is ossified in Portheus and Ichthyodectes. This 

 ossification does not cover the eye, is not a complete circle, and is unseg- 

 mented. 



Little can be said respecting the hyoid apparatus in this family. Some 

 superior branchihyals, preserved in Portheus thaumas, are short flat rods. 

 Two long flat bones, in place between the dentaries of a P. lestrio, appear to 

 be the distal ce'ratohyals. They terminate in some crushed basihyals, and are 

 covered with minute teeth en brosse on the inner faces and superior margins. 



No specimen exhibits the entire scapular arch, but several preserve the 



scapula with adjacent parts ; two, a Portheus and probably an Ichthyodectes, 

 24 c 



