164 DIMYARIA. 



Plate XVIII. figs. 8 and 9. Transversely elongated, un- 

 dulated; concentrically wrinkled; of a yellow-fa vm colour. 

 Inhabits the Mediterranean. 



Genus 66 SOLEN— Zmn^ws. 



Generic Character. — Equivalve, transversely elongated, 

 gaping at both extremities ; beaks very small, always short ; 

 primary teeth small, varying in number, sometimes none, 

 and rarely a pit between them ; ligament external. 



There are three sections in this genus : — * Shells with a terminal 

 hinge ; and anteriorly truncated. ** Primary teeth somewhat dis- 

 tant from the anterior margin. *** Hinge situated nearer the middle 

 than the anterior end. 



Solen Ensis. — The Sabre Solen. Plate XVIII. fig. 

 11. Linear, sabre-shaped, somewhat reflected at the end 

 next the hinge; in each valve a single compressed tooth 

 without laminaa; olive-brown towards the base of the shell, 

 and next the apex brownish-purple. From five to seven 

 inches broad. Inhabits the seas of Europe. 



TRIBE III. PHOLADARIA. 



Valves with accessory pieces ; or widely gaping ante- 

 riorly. 



Genus67.—GA8TROCU(El!fA.—Spengler. 



Generic Character. — Equivalve, somewhat wedge-shaped; 

 with a very large, oval, oblique, anterior opening betwixt 

 the valves, the posterior extremity nearly close ; hinge linear, 

 marginal, and without teeth. 



Gastrochcena modiolina The Modioliform Gastro- 



CH(ENA. Plate XVIII. fig. 16. Oval, thin, brittle, gaping 

 at the side; of alight reddish-brotvn ; inside bluish- white. 

 Three-fourths of an inch long. I ihabits the British coasts; 

 boring into hard substances. 



