SUMMARY. 



Shell— 



The shell is adapted for swimming, in shape, in weight, in the position 

 and strength of the muscle, and in the possession of a large cartilage, and 

 a straight hinge line which will allow rapid movement without great 

 strains or friction. (See pp. 7-1 1, and Figs. 1-7.) 



Mantle. — 



The mantle lobes are supplied with numerous sense tentacles and 

 eyes which are probably of use in detecting enemies ; with nerves that 

 possess ganglion cells ; with infolded ridges that regulate the opening 

 of the mantle chamber when the shell is open and probably serve to 

 direct the current of water thrown from the shell in swimming; and 

 with strong pallial muscles which serve to withdraw the margins of the 

 mantle when the shell is closed. (See pp. 12-16 and Figs. 9, 10, 16, 20 

 and 26.) 



Foot. — 



The foot is comparatively small, split at the end, and possesses a large 

 byssal gland. It is probably not of much service in locomotion. The 

 retractor muscle of the left side only is retained. (See pp. 16-19 and 

 Figs. 8, 10, and 12.) 



Alimentary Canal. — 



The stomach lies near the hinge line surrounded by the liver. The 

 portion of the intestine that leaves the stomach corresponds with it in 

 structure. It seems probable that one loop of the intestine has been 

 overlooked in previous dissections of scallops. (See pp. 19 and 20, and 

 Fig. 12.) 



Labial Palps. — 



Unlike most forms, the palps are ruffled above and below the mouth. 

 The reason for the arrangement is not known. (See pp. 20 and 21, and 

 figs. 10 and 12.) 



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