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teeth ; but the extent to which it enters into the superior arcade of the 

 mouth varies. It is shortest in Empo, and longest in Pachyrliizodus. The 

 premaxillary is greatly extended in Empo, and shortest in Tcthcodus and 

 Sfratodus. The teeth differ from those of the Baurodontida. in their mode 

 of attachment; instead of being inserted by long roots into deep alveoli, they 

 are anchylosed by the base to the alveolar border of the jaw, which may 

 sometimes be elevated on the outer side so as to give the roots a pleurodont 

 attachment. This is the case in the genus Pachyrliizodus. Although a large 

 amount of material representing the forms referred to this family has come 

 under my observation, I have in no case seen any remains of spinous fin-rays; 

 in the pectoral fins in place, in two specimens of Empo, spines are wanting. 



The vertebral column is only known in Empo, where the caudal fin 

 embraces three and possibly four centra, being thus a little more heterocer- 

 cal than Sahno. 



The genera are readily distinguished by the following, among other 

 characters : 

 I. Premaxillary bone with several rows of teeth : 



Palatine teeth numerous, large ; all with pulp-cavity. . . . Stratodus. 

 II. Premaxillary with two rows of teeth : 



Maxillary bone short; dentary with equal large inner 



teeth and outer rows en brosse Empo. 



Maxillary bone very long; one row of equal dentaries. . . Pachyrhizodus. 

 III. Premaxillary with one or no row of teeth : 



A large premaxillary fang ; anterior maxillary and den- 

 tary teeth enlarged ; cutting-edges not opposite ; 

 unsymmetrical - Enchodus. 



Premaxillary toothless ; anterior maxillary and dentary 



enlarged Tctheodus. 



Large anterior tooth with a cutting-edge in front and a 



shorter one opposite and posterior Phasganodus. 



Owing to the fragility of many of the bones of the cranium, their char- 

 acters remain unknown. It is, however, certain that none of the above- 

 named genera present the prefronto-palatine articulation seen in the Sauro- 

 dontidce. For a similar reason, the structure of some of the fins remains 

 unknown. In some of the genera, the body is protected by scuta as well as 

 by scales. 



