46 PECTINID.E. 



PECTEN, Bruguiere. 



* Shell firm, solid, of a porcellanous texture. 



P. OPERCULARIS, Linnaeus. 



P. opercularis, Brit. Moll. ii. p. 299, pi. 50. f. 3, pi. 51. f. 5, 6, and 

 pi. 53. f. 7- 



Animal suborbicular, thick, lentiform; this shape results 

 from the support given to the organs by the powerful central 

 circular adductor muscles ; the colours are very variable, white, 

 pink, fawn, orange and brown; the body, with the amalga- 

 mated ovarium, is a compound of flake-white meandering 

 lines, spots and blotches, and its conical termination is of the 

 palest vermilion to the intenser hues of that colour ; it de- 

 scends from the dorsal to the ventral range, on the anterior 

 side of the great subcentral muscle. The mantle is thin, 

 except at the fleshy margins, and open throughout, with the 

 exception of a short dorsal area; there is not a trace of 

 siphons; it would be too large for the shell if it were not 

 doubled on itself and fixed a little within the duplicature to 

 the shell by very slender muscular pallial threads. At the 

 folding a cord-like margin springs, but the true mantellar 

 margin floats loose, and is considerably within this line ; both 

 are furnished with 2-3 rows of irregularly deposited, conical, 

 white, pointed cirrhi of three different lengths ; those of the 

 inner circle are tinged with brown ; the outer or fixed range 

 has the longest filaments, and in addition 35-10 subglobose 

 ocelli that have pearl-coloured pupils within black circles; 

 these vary in size, and extend at equidistances throughout the 

 peripherial range to the auricles. 



The foot springs from the body just below the palpi ; it is 

 yellowish white, subcylindrical, of small volume, deeply cloven 

 or furrowed, and scoop-shape at the termination; it appears 

 to have no locomotive use, and only to be the vehicle for pro- 

 ducing a byssus for occasional fixation, especially of the young 

 animal. I have seen most of the species thus fixed. 



There are a pair of subcircular branchiae on each side, vary- 

 ing in different individuals to all shades of the colours above 



