80 CONCHOLOGY. 



FAMILY XVIII. 



Pectinides. Seven genera. 



1, Pedum. The Shepherd's Crook. One species. 



The common name was given to this genus from the re- 

 semblance to a French shepherd's crook. The shell is of 

 a regular form ; its lower valve, in which is a sinus for the 

 byssus, is turned up at the edges, and the upper valve falls 

 within it. 



Shell inequivalve, a little eared; apices unequal, distant, 

 rounded, little evident; hinge without teeth; ligament in- 

 serted in an oblique groove, prolonged to the summit, and 

 carried within in a kind of spoonlike cavity. 



P. spondyloideum. The spondylus-shaped Pedum. PL 

 15, fig. 5. 



Ovate, wedge shaped, flat ; superior valve with longitu- 

 dinal striae ; white, granulated, and rough ; slightly tinged 

 with purple near the beak. 



2. Lima. The File Shell. Six species. 



No sinus or notch ; the valves, thick and gaping, form a 

 lateral opening ; the ears are small, but distinct. 



Shell oval, more or less oblique, almost equivalve, with 

 small ears, regularly gaping at the anterior part of the lower 

 edge ; summits anterior and distant ; hinge longitudinal, 

 without teeth; ligament rounded, almost exterior, inserted 

 in a cavity of each valve ; central muscular impression di- 

 vided into three very distinct parts. 



Lima inflata. Lima annulata. 



L. squamosa. L. fragilis. 



L. glacialis. L. linguatula. 



L. squamosa. The scaly Lima. PI. 15, fig. 3, 

 Answers to the above description, with valves ventricose, 

 armed with vaulted scales. 



