54 PALEONTOLOGY OF NEW JEESEY. 



shoulders of the valves being high and prominent. Surface of the valves 

 marked by fine, even, rounded and thread-like radiating strise which maintain 

 nearly the same size throughout by their frequent bifurcations, but are less 

 strongly developed on the right valve. On the sides of the valves the striae 

 curve strongly upward and pass off on the cardinal slopes even within the 

 limits of the auriculations. Ears of the left valve also radiately striate. 

 Besides the radiating strise the shell is closely marked by elevated concen- 

 tric lines which form free projecting edges where the}^ cross the radiating 

 stric^s, which are more strongly developed and often form fine hair-like 

 spines toward the front of the right valves. The bifurcations of the striae 

 mosth^ take place immediately below these concentric lines. Hinge char- 

 acters not observed, but stated by Mr. Conrad to be crenulated. 



The specimen used by Mr. Conrad, in his description of C. hellisculptus 

 was of small size, but its general form, as given on the plate cited above, 

 and its peculiar striations^ leaves no room for doubt as to its identity with 

 those here used. If the genus Camptonectes is to be distinguished by the 

 punctate depressed lines between the strise, this shell ought not to be 

 classed under it, as they show no evidence w^hatever of that feature, like 

 those found in the Jurassic rocks of the Rocky Mountains. In fact the 

 strise on the Jurassic forms are their best distinguishing feature, being 

 formed by impressed lines which are filled with punctures; the strise being 

 flattened on the top, while these are rounded and wirey in character, and 

 closely pressed together, like the strise on shells of the genus Amusium^ and 

 destitute of punctures in the interspaces. From what evidence of the hinge- 

 structure I have seen I do not think this shell possesses the fold or tooth - 

 like ridge characteristic of Camptonectes, and the anterior ear of the right 

 valve is certainly much more like that of a true Pecten than in the Jurassic 

 species, so that from these evidences I am strongly inclined to consider 

 the shell rather a species of Amusium than of Camptonectes, I see no reason 

 for considering Conrad's C hellisculptus as a distinct species from the present 

 one. Mr. Gabb's type specimen is a cast and does not retain any of the 

 surface characters, consequently he could not have known its true generic 

 relations, but Mr. Conrad has seen it with the shell preserved and refers it 



