204 MALACOZOA. TROPIOPODA. LAMELLIBHANCIIIATA. 



rounded ribs, with very numerous thin-edged lamellae, 

 toward the margin rising into triangular spines. Named 

 after Miss Isabella Macgillivray. 



5. Pecten sinudsus. Shell somewhat orbicular, irre- 

 gularly undulated or distorted, with about forty crowded, 

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

 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 Islandicus. 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 obsoletm. Shell triangulari-orbicular, thin, 

 subdiaphanous, little convex, minutely shagreened with 

 divergent striulee 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, flattish, very 

 thin, semitransparent, glossy, smooth ; one side more 

 produced ; the auricles nearly equal in length, smooth ; 

 the colour various. Similis, similar to the last. 



1 1 . Pecten tumidus. Shell suborbicular, flattish, thin, 

 smooth, semitransparent hyaline 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. Lima, a file. 

 JBruguiere. 



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



