189 



pseudoharengus (alewife) ; but, in that species it articulates posteriorly with a 

 process of the ethmoid, instead of the prefontal. In the bluefish (Pomatomus 

 saltatrix) there is a nearer approach ; here, the malleolus articulates with the 

 prefontal and maxillary, but with the latter only by a squamosal joint. The 

 same species betrays a resemblance to. this family in the insertion of the 

 teeth by roots in alveoli, but the roots are much shorter in the living genus. 

 They are also accompanied by a series of foramina on the inner side of the 

 dentary, as in Saurocephalus. 



Six genera are enumerated below as belonging to this family, of which 

 one, Erisichthe, Cope, is placed in it provisionally : 



Synopsis of genera. 



I. Jaws without foramina on the inner face below the alveolar 

 margin : 

 a. Teeth cylindric : 



Teeth of unequal lengths ; some of them greatly 



developed Portheus. 



Teeth of equal lengths Ichthyodectes. 



aa. Teeth compressed, knife-like : 



Teeth of unequal lengths ; some of the anterior ■ 



greatly developed Erisichthe. 



Teeth equal Baptinus. 



II. Dentary bones pierced by foramina below the alveolar 

 border : 



Teeth with subcylindric crowns Saurodon. 



Teeth with short, compressed crowns Saurocephalus. 



There are some other forms to be referred to this family, whose charac- 

 ters are not yet fully determined. Thus, Hypsodon, Agass., from the European 

 chalk, is related to the two genera first named above, but, as left by its 

 author in the " Poissons fossiles," includes apparently two generic forms. 

 The first figured and described has the mandibular teeth of equal length. 

 In the second, they are unequal, as in Portheus, to which genus this specimen 

 ought, perhaps, to be referred. Both are physostomous fishes, and not related 

 to the Sphyrannida, where authors have generally placed them. Retaining 

 the name Hypsodon for the genus with equal mandibular teeth, its relations 

 to Ichthyodectes remain to be determined by further study of the H levestensis. 



