150 



PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



may bo cither hard up for food or in the latter case find it more 

 convenient to starve, and then a reserve supply of food would be 

 very necessary. Besides, many bivalves which are more or less 

 stationary depend for their food supply on the ocean and river currents 

 laden Avith infusoria, minute algm, etc., which certainly vary in 

 quantity with the seasons ; and all known animals when well fed lay 

 up a store of some sort, either for the winter or for the breeding 

 season, so that I see no reason why the Mollusca should form an 

 exception to the rule. 



In conclusion, I would again point out that the crystalline style 

 and the sagitta may be found both in the Gastropoda and Acephala, 

 and that the former may be developed in a special pyloric caecum 

 or lie freely in the gut. They both exercise a protective and prob- 

 ably also a triturating function, whilst the style is furthermore a 

 reserve supply of food material. 



EXPLANATION OF TLATE XT. 



Anatomy of niiile individual of Pterocera, sp ?: the mantle cavity has been opened 

 aloni;- tho rifjht sidii, and the dorsal wall with the attached organs turned over to the 

 left side of the body. 



mouth. 



operculum. 



eye. 



osphradium. 



pericardium. 



penis. 



pedal ganglion, 

 .pleural ganglion. 



pyloric opening. 



pyloric tooth. 



etterent pulmonary vein. 



pyloric portion of stomach. 



rectum. 



renal orifice. 



reno-pericardial opening. 



salivary gland. 



stomach. 



testis. 



tentacle. 



ventricle. 



vas deferens. 



splanchnic ganglion. 



mantle, 

 mucous gland. 



v.d. 



