48 Bulletin American Museum of Natural History. [Vol. XIX, 



times. Three other species, S. hlondeli Pictet, 5. elongatns 

 Pictet, and 5. lattis (Agassiz) are found in the upper Creta- 

 ceous of Sahel Alma, Mt. Lebanon. 



On the block bearing No. 2509 are found written in pencil 

 the words "Yankton, Neb." Professor Cope merely stated 

 that the specimens came from Dakota. The formation and 

 locality are therefore as follows: Niobrara Cretaceous, 

 Yankton, South Dakota. 



ICHTHYODECTID^. 



Saurocephalus Harlan. 



So far as has yet been shown the only difference between 

 Saiirocephahis Harlan and Saurodon Hays is found in the 

 presence in the former of a row of foramina, one foramen for 

 each tooth, placed some distance from the dental border of 

 the jaws, upper and lower, while in Saurodon there is at 

 the base of each tooth a deep notch. In the latter genus the 

 notches are often converted into foramina by the growth of 

 bone across the notch. There can be little doubt that the 

 foramina of Saurocephalus lancijormis originated from notches 

 like those of Saurodon Icamis. Whether or not this difference 

 shall be regarded as sufficient to indicate distinct genera may 

 be a matter of individual judgment. The writer has pre- 

 ferred to retain all the species under Saurocephalus. 



These openings in the bones of the jaws have been called 

 nutritive foramina, and as such Dr. Woodward speaks of 

 them in the final volume of his work on fossil fishes. There 

 can be little doubt that it is through these foramina that the 

 young teeth enter the sockets. The writer has ground down 

 a small piece of a jaw of this genus and found the very young 

 tooth at the bottom of one of these foramina, lying against 

 the functional tooth. As growth occurs, the root of the 

 tooth pushes itself above the foramen, while the blade grows 

 toward the dental border. It is very improbable that any 

 nutrient vessels enter the sockets through these foramina. 

 From Dr. Loomis's memoir I gather that the view here pre- 

 sented is also that of Dr. Rose. 



