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, pl. 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. 
