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 circular 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 oesophagus 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 being 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 



