the present position of the posterior adductor muscle, the muscle 

 that is retained. If this is the case, it becomes evident that the 

 loss of the anterior adductor muscle has been accompanied by a 

 general reduction of the anterior part of the body, so a large part 

 of the body of Pecten is to be considered morphologically pos- 

 terior. This supposition seems to be borne out by the nervous 

 system, and the vascular system of the mantle, as well as by the 

 extent and position of organs. In most forms the margin of 

 each lobe of the mantle is supplied with a posterior and an ante- 

 rior pallial nerve of approximately equal size. These nerves 

 supply the muscles and sense organs of the margins, and, in 

 many forms at least, unite with each other so they form a con- 

 tinuous connection between the cerebral and the visceral ganglia. 

 In Pecten, not only is this the case, but the nerve in the margin 

 of the mantle is joined at intervals for nearly its whole length 

 by nerves from the visceral ganglia (fig. 15). On the other 

 hand, it is joined only in the region of the anterior ear by 

 nerves from the cerebral ganglia. The visceral ganglia are the 

 important ganglia of the animal, and both the cerebral and pedal 

 ganglia are greatly reduced. 



The blood is supplied to the mantle very largely by the pos- 

 terior pallial arteries (fig. 9). The anterior pallial arteries are 

 comparatively small, and while they are connected with the pos- 

 terior pallial arteries, the size and character of the vessels 

 indicates that the junction is probably very near the anterior 

 wing. 



Considering everything, it seems likely that the longitudinal 

 axis of the body could be mofphologically represented by a line 

 drawn from near the hinge extremity of the anterior ear to the 

 middle of the adductor muscle, and that a very small portion of 

 the scallop is anterior. 



The only portion of the scallop that is eaten is the adductor 

 muscle, which is proportionately very large but certainly forms 

 less than one-half of the bulk of the soft parts of the animal. 

 There seems to be no good reason why tTie remainder of the 

 animal should not be eaten. The margins of the mantle are 

 rather tough but not more so than the neck (siphons) of the 

 soft shelled clam. The probable reason that all but the muscle 

 of the scallop is discarded, while in other forms the whole body 



