Stewart.] Cretaceous Fishes. 263 



oiner anderen Gruppe zuzuweisen. Diese Annahme wird noch mehr 

 bestfttigt durch den Charakter der Maxilla und Den tale, die Foramina 

 und die Art und Weise der Aufeinanderfolge der Zahne. Auf Grund 

 der Gleiohartigkeit der Zahne und der aus erordentlichen Aehnliohkeit 

 der Pnvmaxilla rnit derjenigen von Protosphyrcenan dtirfen wir 

 Saurocephalus bis auf weiters in die Familie von Protosphyrcena 

 einreihen." 



I have been unable to discover the similarity between the 

 premaxilla:* of the two genera mentioned above. In fact, they 

 are very widely different, and I am inclined to think that Doctor 

 Crook mistook the predentary for a premaxilla of Saurocephalus. 

 However, this genus is too closely related to Saurodon to be far 

 separated from it, and if one of these genera is removed from 

 this family the other would have to follow. 



As it is evident that these genera cannot be placed in the 

 Pachycormidir, and as some new characters have come to light 

 since Doctor Crook's paper appeared, I deem it advisable to 

 separate these two forms from the original group and place 

 them in a separate family, to be known as the Saurodontidtr , 

 and to use the name Ichthyodectidx to include the three genera 

 XiphactinuSj Ichthyodectes , and Gillicus. 



Concerning the same Saurocephalidae Zittel, it can only be 

 said that even if the name Saurodontidse had been used by Doc- 

 tor Zittel to distinguish his family of ganoid fishes before Pro- 

 fessor Cope applied it to his group, it would have to be 

 abandoned in light of the fact that Cope's family is founded 

 on the genus Saurodon, which would give it priority over another 

 family of the same name. 



In this family the tooth-bearing elements are each provided 

 with a single row of teeth, and the upper border of the mouth 

 is formed by the maxilla and premaxilla. The supraoccipital 

 is raised into a prominent crest and the maxilla is bound to the 

 skull by means of the palatine. 



This family embraced some of the largest physostomous fishes 

 of the Cretaceous period of North America, and from the size of 

 the jaws and the powerful dentition we may suppose that they 

 rivaled the Mosasaurs, the smaller ones at least, in strength 



