MARINE MOLLUSCA OF THE UNITED STATES. 55 



Genus PORCELLANA, Rumphius. 

 Amboin, Rarit. 113. 1705. 

 Klein, Tent. Method., 83. 1753. 

 Cypraa, Liiiu., Syst. Nat., 1173. 1767. 



The Cowries or Cypraeas, as they are generally called, are gene- 

 rally medjum or large size shells with a handsomely painted en- 

 amelled surface, covering and concealing the spire in the adult. 

 This enamel is derived from the lobes of the mantle, which envelop 

 the shell, meeting on the back, where the contact of the margins is 

 indicated by a line of lighter color. In the young shell the spire 

 is prominent, the outer lip thin, and the general appearance is 

 much like that of an Oliva. The animal has the power of par- 

 tially dissolving, and then breaking its shell across the back when 

 it is necessary' to provide room for its growth ; it is, in fact, easier 

 to do this than to absorb the immense thickness of the lips previ- 

 ously to adding to the circumference in the ordinary manner of 

 shell-growth. 



There are about one hundred and fifty species, inhabiting shal- 

 low water near the shore, in warm latitudes, and feeding on zoo- 

 ph3'tes. 



1. P. EXANTHEMA, Linuffius. Fig. 91. 



Syst. Nat., edit. xii. 1172. 1767. 

 Shell elongately ovate, rather thick, extremities slightl}^ trun- 

 cated; back fulvous-brown, ornamented with round white spots; 

 base pale fulvous, teeth chestnut-brown. 



North Carolina^ West Indies. 



A single specimen has been found at Fort Macon, N. C. It will, 

 doubtless, be discovered at other points on the southern coast. 



Genus TRIVIA, Gr.-iy. 

 Desc. Cat. Cypr. 1833, 

 1. T. QUADRiPUNCTATA, Gray. Fig. 92. 



Zool. Journ. iii., 368. 1827. 

 C. rotunda, Kiener, Coq. Viv., 141, t. 53, f. 3. 



Shell rotundately ovate, extremities obtuse, transverselj' very 

 finely ribbed, with a linear dorsal groove ; light rose color, back 

 ornamented with four conspicuous red dots, two on each side of a 

 dorsal groove, alternating one with the other. 



Nortli, Carolina to West Indies. 



