GEOLOGICAL SURVEY OF THE TEERITOKIES. 345 



the crown, or on the inner side of the apex of the thick root. The ab- 

 sorption which followed excavated both the former and the latter, but 

 the crown was evidently first shed. Then the old root disappeared, 

 and the new one occupied the alveolus, leaving a free separation all 

 round. Finally, on the accomplishment of the full growth of the root, it 

 became anchylosed to the alveolus all round. The pleurodont position 

 of the tooth facilitated the shedding of the root very materially. 



The genus Conosaurus, Gibbes, from South Carolina, is perhaps allied 

 to this one. Its dentition is fully described by Leidy, who changes the 

 name to Conosaurops, mainly on account of the inappropriateuess of the 

 Greek laopog to a fish. This word was, however, employed by the an- 

 cients to designate a fish, and the only use made of the word, out of 

 composition by modern zoologists, is' for species of that class, so that it 

 does not seem improper to use it here. 



Three, perhaps four species, left their remains in the strata examined 

 by the expedition. 



EMPO, Cope. 



Proceed. Amer. Pliilos. Soc, 1872, p. 347. 



This genus differs from the last in possessing large canine teeth in the 

 front of the maxillary bone, posterior to which are two series of usual 

 size. The inner or superior of these takes its rise from the canines and 

 has no great extent, while the outer is marginal. Teeth cylindric-conic, 

 and in the type species somewhat incurved. But one species was found, 

 the U. nepaholica, Cope, a fish as large as a pike of forty pounds. 



STEAT0D0NTIDJ3. 



In this group I have arranged several genera, which resemble Enclio- 

 dus, the largest known of its forms. They are phy sostomous fishes, as in- 

 dicated by the relations of bones of the superior arch of the mouth, the 

 absence of spinous dorsal radii, the cycloid scales, and the general re- 

 lationship to ^sox. Agassiz and others have regarded some of them 

 as allied to Sphyrcena; this opinion was probably derived from a con- 

 sideration of the forms of the teeth, which, to some degree, resemble 

 those of Spliyrcenidce and TricMiiridw. This is, however, like many other 

 minor characters, one of those which appear in both of the great groups 

 of osseous fishes. 



The premaxillary is small, and supports a large tooth in Unchodus; 

 in Stratodus it is also short and supports numerous teeth. In Stratodus 

 the maxillary supports a few teeth; in GimoUchthys a larger number. 

 Eelationship to Esox is displayed by Stratodus, which has broad, flat 

 palatine bones, closely studded with teeth in a brush, and where the 

 maxillary teeth are reduced in size and number. The teeth are attached 

 by the anchylosis of the base to the alveolar face of the jaw, resem- 

 bling thus existing fishes, and differing materially from the families of 

 Fachyrhizodontid(B and Saurodontidw, already considered. 



The genera known to me are the following: 

 Premaxillary with numerous small teeth; maxillary with 

 a few of the same; palatines covered with brushes of 



similar teeth, all with pulp cavity Stratodtis. 



Premaxillary'?; maxillary with a single series of large 

 teeth, which have one cutting edge at base and two at 

 apex ; dentary with inner series of large teeth, which 

 do not enlarge distally, and some series of exterior 

 smaller teeth Civiolichthys. 



