370 



PROCEEDINGS OF THE ACADEMY OF 



[July, 



ance (through acceleration) of the shoulder keel and the assumption 

 of a smooth, rounded whorl outline. In other words we have here a 

 striking parallel of an evolutional process which has taken place 

 slowly during geological time and resulted in the change of one species 

 into another, with a change which has been caused by accident in the 

 growth of an individual. 



In this Longport specimen the animal when washed ashore fortu- 

 nately possessed the soft parts intact. A carefull examination of 

 these disclosed no unusual condition other than the fact that the 

 mantle was rounded instead of angulated. The mantle edge was in 

 noway peculiar and the penis, which in the normal male underlies the 

 shoulder angle, was fully developed and exactly similar to that found 

 in other individuals. In fact no peculiarity of the soft parts could 

 be detected which would account for the causes of the change in shell 

 growth. 



'Abnormality in the Soft Parts of F. canaliculatum. — In the specimen 

 just described the absence of a shoulder angle in the mantle and in 



the shell does not seem to 



be connected in any way 



with the underlying repro- 

 ductive organ. Fig. 1 shows 



the character of the normal, 



backward folded penis which 



lies immediately below the 



shoulder angle. Inasmuch, 



then, as we have noted an 



individual with abnormal shell 



reproductive organs, it is of 



attention to another specimen collected by 



the writer which has an entirely normal shell 



but whose reproductive organs are imperfect 

 (fig. 2). In this case the penis is small, not being more than one- 

 fifth the usual length. If this condition had been the result of an 

 injury to the penis we might expect to find traces of its original con- 

 dition at least around its base. This, however, is not shown for the 

 base is small, having about one-half the normal width. We are there- 

 fore justified, it is believed, in regarding this as an instance of arrested 

 development in a particular organ. No other abnormalities in the 

 soft parts were observed and, as stated before, the shell is in every 

 regard similar to that of the normal individual. 



The Penis of F. carica. — Some interesting points in the compara- 



Fig. 1 — Fulgur can- 

 aliculatum Say. 

 Diagram showing 

 the normal male 

 reproductive or- 

 gan. 



Fig. 2 — Fulgur can- 

 aliculatum Say. 

 Diagram showing 

 undeveloped male 

 reproductive or- 

 gan. 



but with normal 

 interest to call 



