V M8& X '] PROCEEDINGS OF THE NATIONAL MUSEUM. 349 



named in honor of Col. Marshall McDonald, the present U. S. Fish Com- 

 missioner, under whose direction the voyage was carried out. 



In this species the " palmettes " or epipodial lobes between the ten- 

 tacles are proportionally larger than in T. Bairdii and have smooth and 

 not fringed edges. The verge is similar but mounted on an onion-shaped 

 expanded base. There is one very short, small, epipodial filament in 

 front of the operculum on each side ; under the operculum are two very 

 small, instead of three long filaments as in T. Bairdii, on each side. 

 The other features are essentially as in T. Bairdii. The renal organ is 

 very exteusive, with a corrugated surface, and seems to empty into the 

 rectum shortly before the latter becomes attached to the surface of the 



mantle. 



Subgenus SOLAR1ELLA A. Adams. 



Solariella infundibulum Watson. 



Plato ix, Fig. 3. 



Trochus (Margarita) infnndibulumW&tson, Challenger Gastr., p. 84, PI. v, Fig. 5; Dall, 

 Nautilus, p. 2, May, 1889; Blake Gastr., p. 380, June, 1889. 



The presence of a verge, or intromittent male organ, has hitherto, 

 among the lihipidogiossate Mollusks, been recorded only in Neritina 

 (Claparede) and certain Limpets. The organ as it exists in Neritina 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 paradooca and Cocculina spinigera, curious deep 

 sea limpets, it was questioned whether they were not peculiarly modi- 

 fied Trenioglossa. 



Since theu, in several deep-sea mollusks, such as Bimula, Margarita, 

 and others indisputably belonging to the Rhipidoglossa, I have found a 

 well-developed verge ; and there is little doubt that the ancestors of this 

 group, as well as of the Tcenioglossa, 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 infundibulum Watson, offers a singular and very 

 interesting special modification of the anterior portion of the epipodium. 

 on the right side, which appears worthy of particular attention. 



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

 external parts, except the eyes, are white. The foot is wide, straight, 

 and double-edged in front, and, as far as one can judge from specimens 

 contracted in alcohol, must have been somewhat pointed or produced 

 at its anterior corners in life. The sides of the foot are nearly smooth 

 below the epipodial line. 



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

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

 the muzzle is smooth, the mouth very small; the oral disk is flat and 

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

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

 as far as the eiids of the true tentacles, and serve as tactile organs, like 



