368 PROCEEDINGS OF THE SCIENTIFIC ASSOCIATION. 
Area centrota Guppy. 
Proceedings of the Scientific Association, p. 175 (Dec. 1867). 
This species was described as a fossil, but I have since as- 
certained that it is likewise living on our coasts, having been 
collected by myself on the shores of the Gulf of Paria, and 
by Mr. Carr on the South Coast. Its umbones are often, 
pink or red, which color is visible inside as well as outside 
and the shell has a hairy epidermis, generally worn off at the 
umbones. Height 17, length 24 mill, The following is the 
original description : — 
“ Transversely subrhomboidal, with a strong wide carina- 
tion running from the umbo to the posterior angle ; ornament- 
ed with many (36-38) squamosely nodose radiating ribs each 
with a fine subsidiary thread-like rib in the nrrrow interstice ; 
anterior margin short, rounded ; posterior margin strongly 
sinuate, angulate above with the hinge-line and forming a 
more rounded angle with the strongly crenate lower margin. 
Hinge-teeth small in the middle of the straight hinge, but 
becoming larger and diverging considerably towards the 
angles ; ligamental area more or less grooved, especially an- 
teriorly.” 
Thracia dissimilis. 
Ovate-oblong, compressed, white, roughened by numerous 
fine granules which are generally arranged in lines radiating 
from the umbo ; transversely excentrically plaited ; anteriorly 
rounded, posteriorly vertically truncate, with a keel (most 
prominent on the smaller valve) running from the umbo to 
the lower posterior angle. Height 27, length 40, thickness 
15 mill. 
This is nearly allied to T. plicata , which Reeve (C. I. 
Thracia, 7) considered it to be. Our shell is rather interme- 
