OPISTHOBRANCHIATE MOLLUSC^A FROM MONTKREY BAY. 



121 



bineil. From above it is rectangular in outline, 3.2 ram. wide liy 3 mm. long by 2 mm. thick. The 

 herniaj)hro<litic ampulla is whitish, slightly curved vertically, the convex face directed downward, 



2.5 mm. long, with a greatest diameter of 0..5 mm. It courses anteriorly along the ventral face of the 

 anterior genital mass in a groove between the nidamental gland and the spermatotheca. Its anterior 

 end curves upward and enters the nidamental gland at its anterior inner face, giving off the spermatic 

 duct and the uterine duct at its entrance. 



Nearly two-thirds of the bulk of the anterior genital mass is made up of the very large, nearly 

 spherical spermatotheca. In sections it measured 0.76 mm. high by 0.93 mm. long in an individual of 



6.6 mm. total length, the transverse diameter in sections of another individual of the same size being 

 0.97.5 mm. It is lined with a single layer of large cubical ciliated cells becoming flattened posteriorly. 

 The uterine and vaginal ducts open into it upon its outer and upper surface close together. The thick 

 walled vaginal duct passes directly outward from it into the vagina, the thinner and shorter uterine 

 duct receives the duct of the oblong-oval spermatocyst and curves directly downward to its origin as 

 a branch of the hermaphroditic ampulla close to the entrance of the latter into the nidamental gland. 

 The spermatocyst is about 0.52 mm. long by 0.22 mm. wide and lies transversely uixni the upper 

 anterior outer face of the anterior genital mass. 



The spermatic duct dilates into a broad thin prostate gland which nearly envelops the sperma- 

 totheca, leaving only a small portion of its ventral surface free. The gland has thin walls and a 

 large, sac-like lumen which passes anteriorly into the vas deferens. The vas deferens courses to the 

 left and at about the median line loops back toward the right, passing straight outward and downward 

 into the muscular penis (prpeputmm). The retracted glans is blunt, cylindrical, of 0.3 to 0.5 mm. in 

 length and about 0.15 mm. in diameter, and is entirely unarmed. 



Habitat: Abundant everywhere along the coast in rocky tide-pools from Monterey to Point Lobos, 

 upon a red sponge which incrusts the under side of overhanging rocks, and with which it is nearly 

 identical in color. Has been taken at all times of the year in apparently equal abundance. The egg 

 bands are of the usual form characteristic of the Dorididse, a narrow flat ribbon attached by one edge 

 in a closely wound coil to the sponge or to the rock, and of the same color as the animal. The spawn 

 of R. ajcnnea Forbes as described by Alder and Hancock (Monograph British Nudibranchiate Molluaca, 

 1848) is white, while in hundreds of cases of that of R. pulchra seen by me it has always been bright 

 red, and has been found at all times during the year. 



Rostanga pulchra differs strikingly externally from the two previously known species of the genus — 

 R. coccinea Forbes and R. perspwitlala Bergli — in lacking the yellowish or whitish area around and 

 connecting the rhinophores, but especially in the structure of the radula and labial armature, as shown 

 in the following tabulation: 



R. perspicillata. 



Color ; Scarlet, sprinkled with black 



spots. Yellowish area around 

 rhinophores and connecting 

 them. 



Rows in radula ! 61-66 



Teeth in row 60-65 



First pleural tooth No denticles on the hook 



Outer pleurse I With 1 long denticle 



Labial armature I A ring of rods in 12-15 rows, in- 



I terrupted above and below. 



Brownish red or brick red, dotted 

 with black spots. White area 

 around rhinophores and con- 

 necting them. 



.51-57 



5D-70 



With 4-6 denticles on hook 



With 1 long denticle 



A ring of 20 rows of rods 



Uniform bright red 

 let sprinkled wit 

 spots. 



Bergh (Mai. Unters., Sup. Heft II, 1881, p. 102) gives the labial armature of R. corcinea as a ring 0.18 

 mm. broad, apparently interrupted above and below and made up of 12-15 rows of closely packed stout 

 rodlets up to 0.05 mm. in length, the most anterior ones with slightly enlarged distal ends. Serial 

 sections of R. coccinea secured at Naples for comparison show this armature as a band of rodlets, clearly 

 interrupted above and below, having a vertical breadth of 0.21 mm., the uppermost rodlets 0.006 mm. 

 in height by the same in width, and increasing progressively in the succeeding rows below to 0.048 

 nmi., the diameter remaining the same. In R. perspicillata Bergh (op. cit., p. 106) the labial armature 

 forms a continuous ring of about 20 rodlets, in the broadest portion reaching 0.05 mm. in length. In 

 R. pulchra, as described above, the elements of the armature are in the form of flattened hooks, over- 



