Pectinidae 47 



The shells are free, equivalve or inequlvalve; equally or sub- 

 equally eared, with a byssal notch under the anterior ear of the 

 right valve; hinge margin straight; hinge has an internal cartilage 

 fixed in a triangular fosse in each valve; some species show small 

 insignificant lateral teeth; umbos central. Surface usually ribbed 

 and margins scalloped; single muscular impression, subcentral and 

 near posterior margin; simple pallial line. Pectens are byssiferous in 

 the juvenile stage and some species retain this quality through adult 

 life. 



Genus PECTEN Miiller, 1776 

 Pect«n33 raveneli Ball PI. 5, figs. 25a, b 



Alt., 40; length, 45; diam., 12 mm. Color varies through shades 

 of pink to purple with a few rare gold-colored individuals. This is 

 one of the "fan shells". Hinge margins straight; ears subequal; umbos 

 flat, central; ventral margin an almost perfect semicircle; upper 

 valve flat with median area slightly depressed, deeply colored with 

 irregular dark markings; about 21 rounded, radiating ribs with 

 wider interspaces, fine concentric growth lines; interior of valve 

 smooth with margin beyond pallial line showing elevated ribs corres- 

 ponding to external interspaces, each rib with a median sulcus; 

 lower valve deeply concave, pink-tinted without, pinkish margin 

 within; ribs with a central groove and wider than those of the upper 

 valve; inequivalve, margin of lower valve extends beyond that of the 

 upper valve. Single muscle scar; simple pallial line. 



Peeten ziczac^^ (Linne) PI. 5, fig. 26 



Alt., 55; length, 55; diam., 13 mm. Color range similar to that 

 of P. raveneli, but with lower valve tinted only toward ears and 

 umbo. Inequivalve, margin of lower valve extends beyond mar- 

 gin of upper valve. Upper — left — valve flat with central concavity; 

 there are about 35 flattened, radiating ribs — alternate ribs more prom- 

 inent; smooth lateral areas of about 8 mm. width; inner surface of 

 valve white, dark border and deep stain about ears and umbo; lower 



^^ Lat., peeten, a comb; dedicated to Dr. Ravenel, conchologist. 



^* Ger., zickzack, origin uncertain; a series of sharp turns in a course. 



