REPORT ON THE LAMELLIBRANCHIATA. '2\i7 



This species appears to be distriljulud in some western parts of the; Metliterrancan, 

 on the coasts of Spain and Portugal, and at the Canary Islands, which is the most 

 southern locality at present known. 



Monterosato changed the name of this species to Pccten commutatus, because 

 Michelotti had, previously to Recluz, designated a fossil form by the name Pecten 

 lAUippU. As that species belongs to Aimissium, a genus which is nowadays usually 

 recognised, it seems a pity to abolish the name by which the present species is so 

 well known. 



Pecten limatuht, Reeve, var. (PI. XXI. figs. 5~5a). 



Pecten limatula, Reeve, Conch. Icon., vol. viii. pi. xxviii. fig. 124. 



Testa tenuis, paulo incequilateralis, interdum obliqua, fere ajquivalvis, mediocriter 

 convexa, pallida, radiis paucis zonisque concentricis dilutissime subroseis picta, superue 

 utrinque umbones roseo tincta. Valvse striis tenuissimis concentricis umbones versus 

 prsecipue conspicuis ornatse, costulisc^ue gracilibus circa quinquagenis minute squamulatis 

 instructse. Auriculae valde insequales (posticis majoribus radiatim costulatis, anticis 

 brevibus ad latera oblique truncatis). Postica valvse sinistrse inferne profunde sinuata, 

 ad extremitatem subtruncata. Uml)ones acuti, parvi, sublsevigati, marginibus lateralibus 

 concavis, postico in valva sinistra denticulate. Pagiua interna nitens, radiatim sulcata. 



This is a thin, delicate shell, rather higher than long, of a somewhat oblique growth, 

 and consequently a little inequilateral. It is of a pale colour, but, being faintly rayed 

 and concentrically zoned with a very light rosy tint, has a general appearance of being 

 of that colour wdiich is heightened into a decided rose tint on both sides of the beaks. 



The valves are only moderately convex, about equally deep, ornamented with about 

 fifty radiating riblets bearing innumerable minute erect scales. Some of the riblets do 

 not extend as far as the umbones, and being situated close to others, impart to them the 

 appearance of l)eing in pairs. Between the costellse the surface is adorned with 

 excessively fine concentric striae, which, however, towards the umbones, are replaced by 

 more distinct elevated lamellae, w'hich do not, however, cross the ridges, which at this 

 part are entirely destitute of scales. The beaks are rather acute, and somewhat glossy 

 near the tip, which consists of a very minute convex vitreous boss. The converging 

 sides, of which the posterior is armed with many minute cornpressed denticles, are rather 

 concave, unequal in length, the anterior being somewhat the longer, and form in the two 

 largest specimens an apical angle of about 100° and in some instances scarcely 90°. 



The ears are very unequal. The anterior are short, obliquely truncate at the sides, 

 and radiately ribbed, the ribs being about seven in number, slightly squamous and verv 

 slender, with the exception of the upper marginal one, which is usually much stronger 



(ZOOL. CHALL. EXP. PART XXXV. — 1885.) Mm 38 



