OWSTHORRANCHIATE MOLLUSCA FROM MONTEREY BAY. 181 



Branchial plumes 5, tripinnate, arranged in a circle, widespreading, deeply retractile within a 

 sheath with high, thin, flaring margin, its edge smooth, its outer surface with small tubercules similar 

 to those of the dorsum. Height of sheath 2 mm., its diameter 6 mm. Anal papilla at right of center 

 of circle of branchiie, bluntly conical. Renal oiieniug inconspicuous, at base and slightly in front of 

 the anal papilla. 



Dimensions of large individual, length (S mm., lireadth .SO mm., height 12-i:^ mm. Widtli of 

 mantle margin 8 mm. 



Internal anatomy: Notfeum thick, somewhat leathery in consistency. Pseudo-peritoneum cul(}r- 

 less. Blood gland pale yellow, flattened, about 5 mm. long by 3.5 mm. wide, its anterior border 

 re.stiiig upon the central nervous system, its left border in contact with the loop of the enlongated 

 pharyngeal bulb. 



Buccal tube cylindrical, white, 3 mm. long, dilating posteriorly into a conical j.i.rtii.n, 4 mm. long 

 by 2.5 mm. broad at its posterior end. From the center of the enlarged inva.L'inaii .1 |..i>tiri..r face a 

 long slender tube, 35 mm. long by 1 mm. wide, describes a loop to the left, con^ti iris Mid.Unly to half 

 its diameter and tlien dilates at the upper margin of the visceral mass into a short, thin-walled tube 

 which loops forward and downward to pass into the cavity of the liver. 



The visceral mass is grayish, cylindrical, about 18 mm. long by 9 mm. wide, its posterior end 

 rounded and deeply gn>nvcd vertically for the retractor muscle of the branchise. The anterior end is 

 obliquely truncated ui.wai.l and liaikward from the left side, the surface thus formed being variously 

 faceted by contact witli Ihe antcjinr genital ma.ss, the upper surface with a deep longitudinal groove 

 fur the esophagus and iiili>tinc. The cavity of the liver is large, centrally placed, with various short 

 cavernous ramiliratii m- •i|Hning into it, and functions as a gastric cavity. 



llermaplinidiiic L'land thin, yellow, covering anterior end and upper anterior half of the liver. 



The hermapliroditic duct is short, about 3 mm. in length, narrow, and leads directly from the 

 anterior border of the visceral mass into its ampulla (pi. .tix, fig. 38 h. amp.), a large, straight, yellow- 

 isli, thin-walled tube lying along the inner border of the nidamontal gland, 7 mm. long by 2 mm. 

 broad, its anterior end recurved and narrowing into a delicate tuln- ninnin'.' ..ntward aliuii; the supe- 

 rior face of the gland for about 2 mm., where it passes into its sul.-tain c, L'i\ Iml: ■'ii a- ii .li.cs so the 

 spermatic branch. The spermatic duct (pi. xix, fig. 38 sp. d. I j.ass.-s .liiv.ily int.. lln- li ii anterior lobe 

 of a large glandular mass of a brownish yellow color, which overlies nearly the whole of the genital 

 mass (indicated in fig. 38 by the dotted line), its lumen large and irregular, receiving branches from 

 the various lobules of the gland. From the antero-median portion of this prostate-like gland the vas 

 deferens appears as a strong white tube, describes a loop forward and pa,sses into the penis. Length 

 of vas deferens about 4 mm., gradually dilating into the penis. The penis (praeputium) is conical, 

 thick, about 3 mm. in length, the everted glans thick, cylindro-conical, about 1 mm. long by 0.6 mm. 

 in diameter, the tip blunt. The whole glans is thickl}- set with a series of strongly-curved hooks 

 arranged in quincunx, about 36 // in vertical height and extending down the vas deferens for about 

 180// (pi. XIX, figs. 39^0). 



Tlie uterine duct is narrow, 2 mm. long, dilating as it nears the point of entrance of the duct of 

 the sperinatocyst and ojicns into the sperraatotheca by a common tube with the vaginal duct (pi. xix, 

 fig. 38a, ». </ ). Spermatoc-yst ( pi. xix, fig. 38 sp. c. ) long, tubular, coiled upon itself at posterior inner mar- 

 gin of the anterior genital mass, about 6 mm. long by 1.25 mm. in diameter, its duct (pi. .xix, fig. 38a 

 sp. c. d.) hmg and narrow, running along the up])er surface of the spermatotheca to its anterior side and 

 opening into the uterine duct. Length of duct of sperinatocyst 5 mm., its diameter 0.5 mm. 



Spermatothet'a ( pi. xix, fig. 38 .■<p. Ih. ) very large, spherical, forming fully one-half the bulk of the 

 anterior genital mass, covercil dorsally by the brownish gland of the vas deferens. From its anterior 

 face the vaginal duct jjasseH outward directly into the vagina without any sharp line of demarcation. 

 Length of vaginal duct about 3 mm., its diameter 1 mm.; length of the vagina 3.5 mm., its diameter 

 2-2.5 mm. 



Z)onopsis/?(f«a is perhaps the commonest nudibranch to be f.)un<l at Pacific Grove, occurring in 

 the tide pools all along the coast at all times of the year, but perhaps most abundantly during the 

 summer months. Its egg bands are in the usual form of a long flat ribbon, about 7 mm. in width, 

 closely coiled, yellow in color and fastened to the sloping sides of rocks or to brown algw, and are 

 also deposited abundantly in the aquarium, in which the animal may be readily kept. Egg-laying 

 may occur at any time during the year, but takes place mainly in summer. 



Type no. 181286 U. S. National Museum. 



