142 BLTLLETIN OF THE BUREAU OF FISHERIES. 



16. Polycera atra MacFarland. 



[PI. XXIX, lig. 22; |.l. XX. liKS. (■■5-72: pi. XXI. figs. 105,111.] 

 Polycera atra MacFarland, op. cit., p. 50. 



Body limaciform, smooth, plump, highest, in front of branchiie, sloping backward to the short, 

 pointed tail. Slightly contracted in front of heart, then somewhat expanded in the slightly flattened 

 head. Head rather high, sloping downward in front, bearing a moderately w'ide horseshoe-shaped 

 frontal margin carrying 4 slender pointed processes (pi. x.'six, fig. 22). At the sides of the rhinophoren 

 this veil is slightly dilated, carries one or two short, pointed, angular processes (pi. xx, fig. 65), and is 

 continued laterally into a more or less elevated dorso-lateral ridge, highest in the region of the 

 branchiie, where it bears one or two compressed, pointed tubercles, sometimes elongated into short 

 processes (pi. .xxix, fig. 22). The conspicu(jus lobe of P. qiiadrilineata is here represented by a low 

 tubercle of varying height. Behind the branchiie these ridges unite in a low median crest to the tip 

 of the tall. 



Gill plumes simply pinnate, 8 in number, nonretractile, tallest in front, and decreasing regularly 

 in size from before backward. 



Rhinophores stout, nonretractile into sheaths, the stalk conical, the clavus club-shaped, perfoliate, 

 slightly inclined backward. 



General body color black (pi. x.xix, fig. 22) , dorsum and sides with numerous rows of yellow spots 

 more or less confluent into continuous lines. The intermediate spaces between these yellow spots in 

 longitudinal series is grayish, as are also the basal portion of the frontal veil and the foot. Frontal 

 processes, tips of rhinophores and dorso-lateral tubercles or processes yellow. Branchial plumes with 

 a series of yellow spots, the tips also of the same color. Foot linear, the anterior angles prominent 

 (pi. XX, fig. 65). Tentacles very short, lobiform. 



Anal opening at summit of low, cylindrical papilla in center of circle of gill plumes. Renal open- 

 ing slitlike, at the right and in front of the anal papilla. 



Reproductive apertures as usual in the genus, on right side midway between the anterior margin 

 of head and branchiie, the penis opening rounded, the vaginal and gland openings guarded by a fold 

 of the skin. 



Size: Length up to 2,S mm., breadth up to 6 mm., height in heart region 7 mm. 



Pharyngeal tube short, pharyngeal bulb nearly spherical, very muscular, its length about 3 mm., 

 breadth 3 mm., height 2.5 mm., the strong cutting face of the mandibles projecting in front and above. 

 Mandibles strong, of a light yellow color, the anterior cutting face very oblique, made up of two 

 portions, the ventro-anterior cutting portion and the dorso-lateral arched wings (longitudinal and 

 transverse portions of Bergh's description of P. qiuidrilineata, 1879, p. 606). The cutting portion, of a 

 deep yellowish-brown color, strong and thick, presents an outer arched shieldlike surface which is 

 strongly marked with concentric lines, indicating the laminated structure clearly seen in section, as 

 in figure 68. Upper anterior ends of the cutting portions approximated, roimded, the lower posterior 

 ends divergent and curved backward and upward. Laterally and above the cutting portion is con- 

 tinued into the arched plate (pi. xx, fig. 67, 6), the anterior margin of which is stronglv concave, its 

 superior and posterior margins rounded. The relation of the two plates is best shown in thfi section, 

 figure 68, taken along the line a 6 of figure 66, from which it is evident that the cutting portion forms 

 the expanded and thickened ventro-anterior border of the dorso-lateral wing. Seen in front view the 

 line of junction of the external face of the wing with the cutting plate forms a clearly defined line, as 

 shown in figure 72, a. 



Radula rather deeply grooved, of a rich amber color in the posterior teeth, deepening anteriorly to 

 a dark brown. Teeth in 9-10 rows, of which the last one is rudimentary, the halves of the rows of 

 teeth in not exactly a straight line across the radula (pi. xxi, fig 111). 



Rhachis naked, not narrow, in width about 0.3 mm. 



Pleural teeth 2 (pi. xx, fig. 69; pi. xxi, fig. Ill), unequal, the first smaller than the second, alike 

 in shape, the stout shaft flattened, slightly concave upon its inner surface, bearing upon its outer margin 

 a br.iad triangular winglike expansion directed toward the median line. The lower end of the shaft 

 rdunded, the upper end bearing a large smooth-edged hook at rightangles to the shaft. Length of first 

 rhachidiau tooth 0.300 mm., of second 0.412 mm. 



