OPISTHOBRANCHIATK MoLLUSCA FROM MONTEREY BAY. 127 



Mantle margin broad, thin, densely spiculate, everywhere widely nverlapiiing the foot except 

 behind, its under surface smooth (pi. xix, fig. 32). 



Foot linear, bluntly pointed behind, in_ front abruptly rounded, bilabiate, the lower lip thick, 

 fleshy, the upper one thinner. Head small, fitting into a depression in ventral surface of mantle, the 

 tentacles short, flattened, blunt, auriform, with a distinct groove on outer margin (pi. .xix, fig. 32) . 



Eliinci]ilH,ii-s ratlifi- laiL'c. ciiMt, diverging, perfoliate with 10-12 leaver, the clavus forming three- 

 fourths of ihctnlal l.'ii-ili oi the (.iLiaii. Rhinophores deeply retractile within low sheaths, the margins 

 of wliirh aiv (hill aial >l.-l.tly tuln-ivular. 



Branchial i>iuuies small, lU-11, u.sually simply pinnate (pi. .xxi, fig. 110), occasionally biiiinnate 

 in part, siireading, completely retractile within low sheath with thin edges. 



Length of large specimen 20 mm., breadth 8-10 mm., and height 3-4 mm. 



Labial disc strongly convex, the opening triangular with the apex directed upward. Labial 

 armature a broad, light yellow band, quadrangular below, triangular on the sides, narrowing toward 

 the top, where it is interrupted, the inner surface of the band everywhere convex. Greatest width 

 0.390 mm. The elements of the armature closely set, slightly curved hooks, bifid at the distal end, 

 with a neight of about 24 mm. (pi. xix, fig. 33).- 



Radula small, broad, 1 mm. long by 0.6 mm. wide, with a vii\ shalhiw median grove. Teeth in 

 77 rows, the last 4 immature. Dental formula 23-1-23. Khachis very narrow, bearing a single series 

 of teeth overlapped by the first pleural on either side (pi. xix, fig. 54). Base of rhachidian teeth large, 

 tlu- hook nearly horizontal, divided into 4-6 long, nearly equal blunt denticles (pi. xix, figs. 34-35). 

 Pleural teeth 23 in number, the first lateral with a stout hook bearing on its inner margin 2-3 large 

 denticles, on the outer margin 4-7 smaller ones (pi. xix, fig. 34). The successive lateral teeth beyond 

 the first increase in height and in the number of denticles upon the outer margin up to 12-15, the 

 inner margin being destitute of them. Toward the middle of the row the denticles become longer, 

 more slender, and the whole tooth becomes saw-like in form (pi. xix, fig. 36). The outer 3 or 4 

 deci:ease in size somewhat (pi. xix, fig. 376), but not so much as in the preceding species. Height of 

 largest lateral teeth 0.054 mm., width of rhachidian tooth 0.012 mm., its length 0.018 mm. 



The peritoneum is colorless and smooth, the blood gland lobulated and closely applied to the 

 central nervous system, over which it lies. The liver is smooth, bluntly rounded behind beneath the 

 branchial opening, slightly dilated about midway of its length and olili.|Ucly tnuicated in front from 

 right to left, the face thus formed being in close contact with the anterior Lrcnital mass. Total length 

 6 mm., its greatest width 3 mm. Midway of the left side of the liver the i>yloric cud of the stomach 

 is ex[)Osed, giving rise to the intestine, which arches across to just beyond the median line toward the 

 right and then jiursues an oblique course backward to the anus. 



The hermaphrodite gland is thick and lobulated, covering incompletely the dorsal, lateral, and 

 anterior faces of the liver. The hermaphrodite duct is very short, dilating into the ampulla, which, 

 passing forward on the lower inner face of the anterior genital mass for about 3 mm., doubles back 

 upon itself, describing a simple loop, and returns jwsteriorly to the anterior inner edge of the oblique 

 face of the anterior genital mass. Here it gives rise to the spermatic duct and opens into the 

 nidamental gland. 



The anterior genital mass is large, bluntly conical in front, lieveled from left to right behind, the 

 flattened face thus formed fitting closely against the oblique auteri'ir face of the liver. Tlie outer 

 surface is convex and made up almost entirely of the niilameiital Lilaiid, 



The spermatic duct, rising from the distal end of the lierma|>liroilitii' aiiiimlla at tlie [loint where 

 it enters the nidamental gland, is a very long, closely coiled tube lying np.^u the anterior end of the 

 anterior genital mass. In it may be distinguished a proximal thicker glandular pnition in a conspicu- 

 ous loop upon the upper anterior face of the genital mass, and a more slender muscular portion, the 

 vas deferens proper passing into the conical penis (prseputium) after describing a double loop upon the 

 anterior face of the genital mass. The glans penis is short, bluntly conical, and is armed with minute 

 recurved hooks, the armature extending for a distance of 1 mm. along the lining of its canal. 



The vagina is sliort, conical, passing over into the very slender vaginal duct which courses inward 

 to the inner olili(jue face of the nidamental gland and passes into the small spherical spermatotheca, 

 alioutO.27 mm. in diameter. Close to its entrance arises the uterine duct, which receives the duct 

 of the small pear-shaped spermatocyst and passes into the nidamental gland. 



Habitat: Found in rocky tide pools all along the coast near Pacific Grove. Not rare. Found at 

 all times of the year in small numbers. Type no. 181279 U. S. National Museum. 



