204 MALACOZOA. TROPIOPODA. LAMELLIBTlANCIilATA. 



rounded ribs, with very numerous thin-edged laraellse, 

 toward the margin rising into triangular spines. Named 

 after Miss Isabella Macgillivray. 



5. Pccten shmdsns. — Shell somewhat orbicular, irre- 

 gularly undulated or distorted, with about forty crowded, 

 unequal, more or less scaly or spinous ribs. Simwsus, 

 winding, or uneven. 



6. Pecten Pusio. — Shell ovate or ovato-oblong, equi- 

 valve, with about forty alternately large and small, re- 

 gular, somewhat nodose ribs, becoming somewhat spinous 

 toward the margin ; one of the ears almost obliterated. 

 Pusio, a dwarf. 



7. Pecten Islandiciis. — Shell suborbicular, subequi- 

 valve, with about forty, crowded, narrow, convex, lamel- 

 loso-striate, subscabrous ribs, which subdivide, so as to 

 amount to more than a hundred toward the margin. 

 Named from being found in Iceland. 



8. Pecten obsoUtus. — Shell triangulari-orbicular, tliin, 

 subdiaphanous, little convex, minutely shagreened with 

 divergent striulse crossed by smaller, variously costate or 

 striate, and varying in colour. Obsoletus, worn smooth. 



9. Pecten Icevis. — Shell orbicular, subtriangular, little 

 convex, very thin, semitransparent, glossy, smooth ; the 

 two sides equal ; the auricles unequal, radiatingly stri- 

 ated ; the colour various. Lcevis, smooth. 



10. Pecten similis. — Shell orbicular, ilattish, very 

 thin, semitransparent, glossy, smooth ; one side more 

 produced ; the auricles nearly equal in length, smooth ; 

 the colour various. Shnilis, similar to the last. 



1 1 . Pecten tiimidus. — Shell suborbicular, flattish, thin, 

 smooth, semitransparent hyahne toward the margins, 

 opaque-white in the centre ; one side tumid, or much 

 produced and rounded. Tumidus, swollen. 



Genus 2. Lima. — Shell free, oval or oblong, equivalve, 

 anisomeral, thin, fragile ; the hinge-line straight ; an 

 external triangular depression for the ligament ; the 

 valves radiatingly striate or costulate. LimOy a file. 

 Bruguiere. 



1 . Lima Loscdmbi. — Shell obliquely oval-oblong, tumid. 



