28 PALEONTOLOGY OF NEW JEESEY. 



narrower hinge-plate, and more delicate and slender teeth, while the shell 

 is proportionally broader along the basal margin, the valves much more 

 ventricose, and the beaks more distant. It is possible the generic features 

 of this shell may not be exactly those of the modern Gnathodon, but so far 

 as can be seen on all the specimens examined there seems to be no reasonable 

 doubt of their generic identity. The specimens are all highly imperfect, so 

 much so that the generic features, as exhibited on the hinge-Hne, cannot be 

 illustrated; and, of course, under such circumstances, it is difficult, if not 

 impossible, to determine definitely the generic relations. The only part of 

 the original substance of the shell preserved on the specimen is the epider- 

 mis, which is very distinct on some of them, and a little of the oxide of iron 

 which has replaced the original shell. On one of those figured there is the 

 remains of a species of Flustra and fragments of Serpula^ showing its habitat 

 to have been in sea water. 



Formation and locality. — The specimens are from the clay beds below 

 the Lower Marls, at Sayre's and Fisher's brick-yards, and at R. N. and H. 

 Valentine's, near Woodbridge, New Jersey. The specimens are in the 

 State collection at New Brunswick and that of Columbia College School of 

 Mines in New York. 



