78 DR JOHNSTON'S CATALOGUE OF BIVALVED SHELLS 



PBCTENID/B. Pecten obsoletus. 



Pecten maxiinus. spinosus, Brown, Ittus. pi. 33, 



opercularis. fig. 8. 



lineatus. Lima fragilis. 



varius. 



II. DIMYAIRIA. 



ARCADE. Tellina fabula. 



Area fusca. tenuis. 



Nucula nuclea. crassa. 



mi nut n. Psammobia florida. 



Ferroensis. 



MYTILID.K. solidula. 



Mytilus edulis. Cyprina islandica.* 



var. pellucidus. Mactra solida. 



var. subsaxatilis, Williamson, in truncata. 

 Mag. Nat. Hist. vii. p. 354, subtruncata. 

 fig. 48. elliptica, Brown, Illus. pi. 15, 



Modiola vulgaris. 1 fig. 6. 



var. barbatus. stultorum. 



discors. Kellia suborbicularis. 5 



discrepans. 2 rubra. 



Cyclas corneus. 6 



UNIONID^;. amnicus. 



Anodon anatinus. Pisidium pulcliellum, Jenyns. 



cygneus. pusillum, Jenyns. 



Astarte Danmonise. 



CONCH ACE JE. Scotica. 



Cardium edule. compressa. 



echinatum. 3 Cytherea exoleta. 7 



laevigatum. lincta. 



Donax trunculus. ovata. 



1 Lamarck has arranged " Modiola'' amongst the " Monomyairia, " but M. vulgaris has 

 three or more properly four, adductor muscles ; viz. one near each end of the shell, and two 

 lesser ones towards the centre of the body. 



2 The foot of this and the preceding is very extensible, and when extended, is several 

 times longer than the shell, and almost filiform. By fixing this foot at the furthest point to 

 which it can be stretched, and then dragging the shell forwards, the animal moves with con- 

 siderable rapidity ; and swims readily in a reversed position on the surface. . 



3 Foot of a rich pink colour, long, somewhat compressed, with a bend or elbow, whence 

 it tapers to an obtuse point : cloak with a plain thin margin, about a line in breadth, behind 

 which it is suddenly thickened, and at regular intervals raised into glandulous warts or tu- 

 bercles, corresponding to the grooves in the shell : respiratory and excrementitious aper- 

 tures encircled with tentacular filaments ; labial appendages long, strongly striate on one 

 side. 



4 Animal white ; the cloak open, with a thickened minutely crenulate border, the ori- 

 fices of the passages encircled with papillae ; foot broad, compressed, the margin plain, and 

 somewhat undulate. 



5 Animal clear white ; syphonal tube single, cylindrical, with a plain aperture ; foot 

 compressed, tapered, thin, and flexible. 



6 Often found in marl. 



7 Animal with a broad compressed foot ; syphonal tubes united throughout, with plain 

 apertures. 



