EAST COAST MARINE SHELLS 



29 



Foot of animal crescent shaped; 

 margins simple, with minute eyes. 



GLYCYMERIS AMERICANOS Def ranee (G. undatus 

 of authors) . American Bitter-sweet. There 

 are two sorts of modifications present in 

 this species. One is due to variation, 

 the other correlated with growth and senil- 

 ity. Very young shells show indistinct 

 sculpture, half-grown ones ribs well marked 

 and teeth delicate. In adults the ribs be- 

 come obscure distally, the cardinal tooth 

 area enlarged. In senile individuals the 

 cardinal tooth area is very large, only the 

 teeth at the extremities of the arch re- 

 maining and these enlarged, the concentric 

 sciilpture strong. With these facts known 

 the apparent great variation of the shells 

 can be explained. Diam. 29 mm. Depth 

 range 15-65 fathoms. 



PI. 2, Fig. 12 



Cape Hatteras, North Carolina to 



the West Indies 



GLYCYMERIS AMERICANOS LINEATUS Reeve. 

 Lined Bitter-sweet. This, the Antillian 

 form is not uncommon and averages smaller 

 than the preceding typical one. 



In all forms of G. americanus the 

 reticulated sculpture is always present 

 upon the umbones of a perfect shell, the 

 extension of the reticulation varying with 

 the individual. Specimens from southern 

 waters are more swollen and brightly col- 

 ored than northern examples. Length 1.5 

 inches. 



PI. 2, Fig. 6 



North Carolina to the West Indies 



and west to Texas 



GLYCYMERIS PECTINATUS Gmelln. Comb Bitter- 

 sweet. Shell fan-shaped, solid, hardly in- 

 flated; usually about twenty-four rounded, 

 curved, ribs, sometimes as many as forty, 

 crossed by fine striae; teeth feeble or ab- 

 sent near umbones; margin of shell crenu- 

 lated; color white, spotted with brown, 

 sometimes in zigzag pattern. Length 20 mm. 

 Depth range 2-175 fathoms. 



PI. 2, Fig. 8 



PI. 64-, Fig. 16 ■ 



Cape Hatteras, North Carolina to 



West Indies and west to Texas 



GLYCYMERIS PENNACEDS Lamarck. Feathered 

 Bitter-sweet. Shell solid, somewhat swol- 

 len, umbones high and full; ligament strong; 



surface with wide, low, radiating ribs 

 which together with the spaces between are 

 covered with fine radiating lines; concen- 

 tric growth lines fine and variable, form- 

 ing a latticed surface; velvety epidermis 

 often lacking around umbones or on dead 

 shells. 



In Florida the shells attain a 

 length of about 29 mm. The species may be 

 separated from the others by the almost 

 smooth surface and angular outline. 



PI. 8, Fig. 7 



PI. 2, Fig. 7 



Florida and the West Indies 



Family Plnnldae 



Shell wedge shaped, gaping on pos- 

 terior end; hinge teeth present. Animal 

 spins a powerful byssus and is fastened by 

 large triple muscles to middle of each 

 valve. 



The Pin- 

 na s with knife- 

 like ends pointed 

 upward and, al- 

 most burled in 

 mud or sand, are 

 a menace to bare- 

 footed shell col- 

 lectors. When 

 young the shells 

 are extremely 

 thin, brittle, 

 translucent, and 

 Fig. 31 consist almost en- 



Cellular Structiire tlrely of prismat- 

 of Pinna ic layers. Gloves 

 have been manu- 

 factured by combining the byssus with silk 

 and specimens are on exhibition in the 

 British Museum. 



Some of the species attain a length 

 of two feet. A small crab lives in the 

 gills and mantle and was noted by Aristotle 

 who named it the Pinna guardian. The cel- 

 lular structure is shown in Fig. 31. 



GENDS PINNA Linne 1758 

 (SEA PENS) 



Shell sulcate longitudinally or 

 with a middle keel. 



PINNA CARNEA Gmelln. Flesh Pen. Each 

 valve has about eight strong ribs and less 

 distinct ones between; color orange or 



