LAMELLIBRANCHIATA OF THE LOWER MARLS. 57 



shell has been mentioned and I'eferred to. Judging from what specimens I 

 have examined, there appears to be but little reason for considering them 

 other than as varieties of a single species, and our American forms diifer so 

 little from those found in Europe and Asia that I have been inclined to 

 refer them back to the place where Dr Morton first placed them. The 

 generic reference of the form seems to have passed through equally great 

 tribulation as the species. I have left it under the genus which most writers 

 of late date seem to prefer, as there is some doubt as to the exact value of 

 the two older names Vola Klein, and Janira Schum. 



Formation and locality. — In New Jersey it is found in the Lower Green 

 Marls at Burlington, Holmdel, Freehold, and Mullica Hill. It is also 

 found at Prairie Bluff, Ala., and at several places in Texas, and in Eng- 

 land, Continental Europe, and at many places in Asia, being one of those 

 almost universal forms which we occasionally find. 



SPONDYLID^. 



Genns SPONDYLUS Lam. 



Spondylus gregalis. 



Plate IX, Figs. 11, 12, and Pliite X, Figs. 1,2. 



Plagiostoma gregale Morton. Synop., p. 60, PI. V, Fig. C. 



Spondylus gregalis (Mort.). Gabb, Synop., p. 171. Meek, Check -list Smith. Inst , p. 7. 



Geol. Rept. N. Jer., 18C8, p. 724. 

 S. gregalis D'Orb. Prod., p. 254. 



Shell rather above medium size when fully grown, and generally ovate 

 in form, with the lower or attached valve somewhat the deepest. Cardinal 

 area large, but short, much extended and flattened on the surface; trans- 

 versely striated, and with a narrow linear groove through the middle; teeth 

 strong. Surface of the lower valve strongly lamellose on the free 2)ortions; 

 the attachment apparently being only small and near the apex; between 

 the lamella, which are elevated, the surface shows indistinct radiations, 

 which on the interior are quite distinctly marked and flexuose, and are 

 comparatively fine. The upper valve not observed, except as shown on 

 casts of the interior. In this condition it is shown to have been only very 



