138 Sellards — Nero Gavial from Late Tertiary of Florida. 



Tomistoma americana. sp. n. 



The species Tomistoma americana is based upon the anterior 

 part of a skull, including the rostrum, from the Bone Valley 

 formation of Florida. The rostrum is much elongated and 

 shows a very slight upward curvature. The teeth, of which 

 the base or sockets of eleven are preserved, are sub-equal in 

 size showing but slight differentiation. The premaxillaries 

 extend on the dorsal surface of the rostrum to a point opposite 

 the third maxillary tooth. The nasals are narrow and are 

 wedged in between the backward projections of the premaxil- 

 laries, reaching forward to a point opposite the first maxillary 

 tooth, the nasals and premaxillaries being thus in contact from 

 the first to the third maxillary tooth, or a distance of 10 cm . 

 The notch which should receive the first mandibular 

 tooth is feebly developed being scarcely perceptible. The 

 notch or constriction in the jaw which received the fourth 

 mandibular tooth is, however, well developed. Five teeth are 

 present in each premaxillary, the second, which has dis- 

 appeared from the more specialized species of Tomistoma, 

 being in this species well developed, although slightly smaller 

 than the first, third and fourth premaxillary teeth. The first 

 three maxillary teeth are strong ; the fourth, however, is 

 reduced and the jaw at this point is slightly constricted for the 

 reception apparently of two strong mandibular teeth. Back of 

 the fourth maxillary tooth the rostrum is again expanded, the 

 fifth and sixth maxillary teeth being strong. Between these 

 teeth is seen a distinctly marked pit for the reception of a 

 mandibular tooth. The sockets for the teeth are directed 

 forward. Although none of the large teeth are preserved, the 

 crowns of young teeth may be seen in several of the sockets. 

 These young teeth show keels. On the young first maxillary 

 tooth the keels lack but little of being on the anterior and 

 posterior sides of the tooth ; while those of the fifth and sixth 

 maxillary teeth are more nearly lateral in position. The type 

 of the species is specimen No. 3657 of the Florida State 

 Geological Survey collection. 



With this specimen is associated a fragment of a lower jaw 

 (No. 2372) which is probably of this species and accordingly 

 may be designated as the paratype. This fragment on which 

 is seen the sockets of six of the mandibular teeth is of interest 

 since it shows that the splenial takes part in the mandibular 

 symphysis, a feature common to the gavials, but exceptional 

 among the alligators and crocodiles. 



Florida Geological Survey, 

 Tallahassee, Fla. 



