POLYCLAD FLATWORMS — ^HYMAN 585 



Family Euryleptidae 



Acerotisa rugosa^ new species 



Figures 15a-c; 16a 



Material :SLx specimens were taken by the Stanford team in the 

 Palau Islands at Stations 28, 69, 92 (two lots), 220a, and 236 dm-ing 

 July, August, and October 1955. 



General characters: The form is oval (fig. 15). Three of the 

 specimens (from Stations 69, 92, and 236) were extremely small, less 

 than a millimeter in length. These are devoid of any signs of repro- 

 ductive organs and have an eye pattern typical of juvenile Acerotisa. 

 The specmien from Sta. 92 is shown in figure 15a. It is 0.9 mm. long, 

 has one large and one small eye in each marginal group, and four eyes 

 in each cerebral gi"oup, of which three form a row immediately in 

 front of the pharynx. An identical eye pattern occurs in the specimen 

 (also 0.9 mm. long) from Sta. 69 except that each marginal group 

 includes an additional small eye. The smallest specimen, from Sta. 

 236, measures 0.6 mm. in length and also has four cerebral eyes on 

 each side, but the group of three is in front of the single eye; there 

 are four marginal eyes on each side. The three remaining specimens 

 are all of larger size and show increase in eye number and varying 

 degrees of sexual maturity. The specimen from Sta. 28 is shown in 

 figure 156. It is 1.4 mm. long and has seven to eight cerebral eyes on 

 each side and five eyes in each marginal group. The female gonopore 

 and the male copulatory apparatus are evident in this specimen; the 

 latter is seen under the posterior half of the pharynx in the figure. 

 Another worm of about the same size, 1.5 mm. long, from Sta. 220a, 

 has eight cerebral eyes on one side, 10 on the other, and a total of 

 about 30 marginal eyes, distorted out of their normal positions. 

 Finally, the largest specimen, from Sta. 92, measures 5 by 3.5 mm. 

 It is fully mature and presumably represents the maximum size of 

 the species. Its cerebral clusters contain 9 eyes on one side and 11 

 on the other, and there are about 17 eyes in each marginal group 

 (fig. 15c). 



All specimens have a rugose dorsal surface caused by bundles of 

 rhabdites which tend to form little pointed projections, as shown in 

 the small turned back fold on the upper left of figure 15c. There are 

 also evident in the largest specimen flask-shaped glands along the 

 periphery, although these are not as regularly and closely arranged 

 as in Acerotisa multicelis Hyman (1955a). 



The small specimens appear colorless or pale but the largest one is 

 reddish brown. The position of the sucker is shown in the figures; 

 it was much distended in the specimen depicted in figure 156. The 



