THK XAUTILUS. 



NOTES ON THE SOFT PARTS OF TROCHUS INFUNDIBULUM WATSON 



With an account of a remarkable Sexual Modification of the 

 Epipodium. hitherto undescribed in MoUusca. 



15Y WSl. ir. ])ALL, CURATOR DKPT. OF MOLLUSKS, U. S. NAT. MUSEUM. 



The prei^ence of a verge, or iiitroiuittent male organ, has lutherto, 

 atjiong the Rhii)hi(logh)ssate Mollusks, beeu recorded only in Xer- 

 itina (Claparede) and certahi Limpets. The organ as it exists in 

 Xeritina and Nerita, is so short and obscure that its function and 

 even its existence has been called in question. "When I showed its 

 existence in the rather anomalous Addisonia parndoxa and Coceidina 

 spinigera, curious deep-sea limpets, it was questioned whether they 

 were not peculiarly modified Tcenioglossa. 



Since then, in several deep-sea Mollusks, such as Bimula, Marga- 

 rita and others indisputably l)elongingto the Bhiphidoglossa, I have 

 found a well-developed verge; and there is little doubt that the an- 

 cestors of this group, as well as of the Teetiioglossa, were so provided, 

 and that some of these deep-sea forms have retained the organ now 

 generally obsolete in their shallow water congeners. In combination 

 with this survival, one of the species, Trochus infundihnlum "Watson, 

 offers a singular and very interesting special modification of the an- 

 terior portion of the epipodium on the right side, which appears 

 worthy of particular attention. 



The soft parts of this species afiTord several notes of interest. The 

 external ])arts, except the eyes, are white. The foot is Avide, straight 

 and double-edged in front, and, as fsar as one can judge from speci- 

 mens contracted in alcohol, must have beeu somewhat pointed or 

 produced at its anterior corners iu life. The sides of the foot are 

 nearly smooth, below tlie epipodial line. 



The nuizzle is small and slender at its proximal end, enlarged and 

 transversely semi-lunar at its distal extremity. The oral surface of 

 the nuizzle is smooth, the mouth very small ; the oral disk is flat 

 and produced on each side into a thin linguiform lappet, with simple 

 and entire edge. These lappets are remarkably long, their ends 

 reaching as far as the ends of the true tentacles, and serve as tactile 

 organs, like the oral tentacles of the Lepetldce, or the much smaller 

 lappets of AcmcBa. "When not feeding, or seeking food, these lappets 

 would seem to be applied to the sides of the foot below the epipodium. 



