TETHYS—WEST AMERICAN, 89 
species seems very nearly allied to this, unless it be the Antillean 
form of T. dactylomela. 
T. RoBERTsI Pilsbry, n. sp. PI. 55, figs. 4, 5. 
Length (of alcoholicspecimen) 11 em. General form slender and 
lengthened ; the tail unusually long, depressed, and extending far 
beyond posterior insertion of the swimming lobes. Neck and head 
elongated, the mouth in a vertical fissure as usual. Rhinophores 
conical, slit abuut half-way down, the minute, rudimentary eyes 
situated outward from them, but only a trifle anterior to the front 
of their bases. Swimming lobes wholly free from anterior to posterior 
insertions, moderately ample. Mantle having a minute, subcentral, 
conic tube; its free right border wide, produced in a folded lobe 
posteriorly, forming a rather long excurrent siphon. Opaline 
gland opening by a single large orifice. Foramen of the penis situ- 
ated far forward, anterior to and below the right anterior tentacle, 
above the front edge of sole. Foot fleshy, the sole wide, emarginate 
in front. 
Color (in alcohol) dirty light olive, very minutely wrinkle-retic- 
ulate with black-brown in places, forming a large cloud on the out- 
side of each swimming lobe, another occupying the face ; sole black- 
ish ; inner surface of swimming lobes blackish below, lightly stained 
in places outwardly. Mantle clear olivaceous over the shell, the 
free border and siphon blackish. 
Shell thin, fragile, with very slight calcareous layer ; buff outside ; 
apex hardly curved, with a narrow reflexed margin. Sinus long, 
nearly straight, margined. Length 28, width 22 mill. 
West coast of Mexico (Dr. W. H. Jones). 
Notable features of this species are the unusually posterior eyes, 
anterior male genital pore, wholly free swimming lobes, and especi- 
ally the long tail. The shell has a very thin calcareous layer, and 
the sinus is nearly straight. The type wasin a bottle with Dolabella 
californica Stearns, which it resembles in color, at least in the 
alcoholic condition. The specific name is in honor of Mr. S. Ray- 
MOND RoBeErRts, whose services as an officer of the Conchological 
Section during a long series of years, are well known and appreciated 
by conchologists. 
T. CALIFORNICA Cooper. PI. 56, figs. 13, 14. 
Length 373, breadth and height 123 cm. (Cooper). Length of 
alcoholic specimen described below 11 cm. Body obese, the ante- 
