OF THE UNITED STATES. 69 



tenautx, Sowerby ; but a few opportunities of examining 

 casts of the contained bivalve, induce me to consider it a 

 much more elongated, angular and compressed shell, 

 than that represented in Mr. Sowerby's figure. 



Of frequent occurrence in both divisions of the creta- 

 ceous group in New Jersey. In the calcareous strata its 

 shelly tube is often replaced by crystallized carbonate of 

 lime. In the friable marls it is mostly observed in casts 

 in lignite : these remains are sometimes pyritous, and half 

 an inch in diameter. 



Clavagella, Deshayes. 



C. armata, (S. G. M.) PI. ix, fig. 11. 



Specific character. Disk obtusely compressed, divided by 

 an irregular fissure, and armed with four or five tubular spines; 

 two or three other spines below the disk ; bivalve concentric- 

 ally furrowed or striated. 



This first American species of a rare and curious ge- 

 nus, differs in several respects from the C. coronata of 

 Deshayes, (Sowerby, pi. cccclxxx,) as in the number and 

 arrangement of the spines &c. One valve is obviously 

 attached to the shelly tube ; but I cannot ascertain 

 whether the spines in my specimen have been branched, 

 as in the European species. 



First found in the friable arenaceous marl near Arney- 

 town, N. J., by Mr. T. A. Conrad; and more recently 

 by the same gentleman at Prairie Bluff, Alabama. 



