OI'ISTHUBRANCHIATE MULLUSCA FROM MONTEREY BAY. 



148 



Uncinal teeth 3, triangular prismatic in form, decreasing in length and width from within outward. 

 Each bears a sharp crest upon the upper two-thirds of its inner border, from which the upper sur- 

 face slopes outward, the inclination decreasing in the second tooth and nearly disappearing in the 

 third. Li)\ver end of the uncini rounded, the upper triangular and sloping inward. Length of first 

 uncinu.-- 0.202 mm., of second 0.16.5 mm., of third 0.099 mm. Occasionally a rudimentary fourth uncinal 

 tooth may be found (pi. xx, fig. 70), but this is of rare occurrence. 



Nervous, vascular, and digestive systems present no striking distinctive characters different from 

 the other species of the group. 



Blood gland irregularly lobulate, lying upon aorta at anterior end of the genital mass. About 

 1 mm. long, 2 mm. wide, and 1 mm. thick in large individuals. 



Reproductive system: Ovotestis thin, covering the whole of the liver. Hermaphrodite duct deli- 

 cate, thin-walled, short, its ampulla not long, its walls thicker, slightly dilated, dividing at anterior 

 face of nidameutal gland into spcnuatic duct and oviduct. Spermatic duct short, looped in close con- 

 tact with nidameutal gland and passing into the large prostate gland, which is made up of a flattened 

 loop of the glanilular tube, the whole closely bound together in the form of a concave disk of about 2 

 mm. diameter, lying upon the anterior face of the spermatotheca. From its anterior end is given off 

 the narrow vas deferens, about 0.2 mm. in diameter and 5 mm. long. No ampulla other than a very 

 slight dilation of the duct is to be found (pi. x.xi, fig. 105 amp). Glans penis truncately conical, 

 closely set with minute, curved teeth, the largest 8/( in height by 2.5 /z wide (pi. x.x, fig. 71), arranged 

 in rows, the total length of the armature in the retracted glans and the vas deferens together being 

 about 1 mm. Vaginal duct and uterine duct given off from a common duct, about 0.1 mm. long at the 

 outer side of the spermatotheca. The very narrow, thin-walled uterine duct receives the 0.4 mm. long 

 duct of the spermatocyst and doubles its diameter, and after a course of about 3 mm. opens into the 

 spermatotheca, for the last half of its length being closely attached to the vaginal duct. Spermatocyst 

 (pi. XXI, fig. 105 sp. c. ) ellipsoidal, 1 mm. long, 5 mm. broad, its duct extremely narrow. The sperma- 

 totheca (pi. XXI, fig. 105 sp. th.) large, about 2 mm. in diameter, spherical, on lower median side of the 

 genital mass forming one-half of its total volume. The vaginal duct, about 5 mm. long and 0.3 mm. 

 in diameter, gradually dilates at its distal end into the vagina. 



Habitat: On brown alga; in rocky tide pools from :Monterey to Cypress Point. Kspecially abun- 

 dant at Point Alones (Chinatown Point). Common. 



The structural characteristics of Polycera atra clearly separate it from any other species of Puli/cera 

 hitherto described. The low extrabranchial appendages resemble those of Palio pallida, described by 

 Bergh ( bSSO) from Alaskan waters, but the coloration, the long frontal processes, the mandibles, radula, 

 and reproductive apparatus are all decidedly different. 



Type no. 181278, U. S. National Museum. 



RaduUv of Kpecies of Poli/cera, and Palio. 



Subfamily XII. GONIODOEIDINai, 



Body oval, more or less dejiressed, pallial margin strongly prominent; or elongate, sometiujcs 

 liuiaciform, the dorso-lateral margin sometimes with simple appendages. Rhinophores often with 

 sheath, retractile or non retractile, the clavus parfjliate; branchi« rarely of few plumes, usually of 

 many, the plumes usually simply pinnate, rarely tripinnate, often arranged in liorseshne form. Ten- 

 tacles small, lobiform; the foot usually wide, rarely narrow, rounded in front or with prominent angles. 



