FAMILY 4. PECTINACEA. 157 



passage of a byssus, nor does it at all correspond with it in structure ; 

 but its affinity in every respect with that of Pecten appears remarkable. 



It may be described as being longitudinal, nearly equivalve, auricu- 

 lated and gaping on one side. The umbones are divergent, their internal 

 facets being inclined outwards. The hinge is edentulate ; but the mar- 

 gin is sometimes indistinctly crenulated on both sides. The ligament is 

 partly external, inserted in a triangular pit in the centre of the oblique 

 area. The muscular impression is inclined towards the side. 



The shell of Lima is always white, covered with a brown horny epider- 

 mis. The valves are for the most part disposed in ribs, diverging; in 

 symmetrical order from the umbones to the margin, generally more or 

 less imbricated externally. 



Examples. 



PI. CXII. Fig. 1 . 



Lima glacialis, Lamarck, Anim. sans vert., new edit., vol. vii. p. 116. 



Enc. Me'th., pi. 206. f. 2 and 3. 

 Ostrea glacialis, Gmelin. 

 Ostrea scabra ? Born. 



PI. CXII. Fig. 2. 



Lima squamosa, Lamarck, Anim. sans vert., new edit., vol. vii. p. 115. 



Enc. Meth., pi. 206. f. 4. De Blainville, Manuel de Malacologie, 



pi. 62. f. 3. 

 Ostrea lima, Linnaeus. 



Pi. CXII. Fig. 3. 



Lima bullata, Sowerby, Genera of Shells, No. 17. Chemnitz, vol. vii. 



t. 68. f. 6496. 

 Ostrea bullata? Born. 



PI. CXII. Fig. 4. 



Lima Loscombii, Sowerby, Genera of Shells, No. 17. 

 Pecten Loscombii, Leach. 

 Pecten frayilis, Montague. 

 Pecten subauriculata, Montague. 



