PECTEN. 47 
named, deep, and of similar depth, very thin and delicately 
reticulated ; the outer surfaces of each pair, as in Anomia, 
with which Pecten has alliances, are doubled on each other, 
and form cireular pouches when in natural position ; but these 
duplicatures can be put straight and again returned. In 
connection with them, on each side, are a pair of broad short 
palpi, rounded at their extremities, fixed laterally to the body 
and to each other, so that they fold as the leaves of a book ; 
they are smooth without and well pectinated within, of a 
yellow-brown or pale orange colour; each pair is united with 
the other around the mouth by two cordons of 5-6 short, dull 
orange, fimbriated cirrhi; the mouth is between them, and 
passes by a short cesophagus into the stomach, which is im- 
mersed in the extremely dark granular liver, and contains the 
usual stylet and attritor or tricuspid membrane ; the intestine 
plunges to the bottom of the body, and again ascends to the 
dorsal line passing around, embraced by the heart and becoming 
fixed to the posterior side of the great muscle, debouching 
at nearly the ventral level. The ovarium is mixed up with 
the body ; its surface is studded with ova, and the vermilion 
termination contains a milky fluid which may be the fecun- 
dating influence; it is only in the genial season that this 
appearance is seen. We have no faith in the doctrine of the 
bisexuality of the Acephala; in many it is impossible for a 
contact to ensue. 
The locomotion is effected by the animal with the posterior 
end in front suddenly opening and closing the valves, which 
action, as we have repeatedly witnessed, produces a motion as 
rapid as that of a Lobster or a Sepia. 
This species bemg more universally distributed than any 
other, may be considered as the type of the British Pectines, 
in which the organs present almost an identity of form. The 
specific differences consist chiefly in the colours, and in the 
arrangement and size of the cirrhi of the margins of the 
mantle, together with a general but unmistakeable aspect in 
each species, which affords the practised eye sufficient di- 
stinctive characters ; but if the younger student is at a loss to 
appreciate the animal specialties, he will obtain much aid from 
