414 University of Calif ornia Puhlications in Zoology [Vol. 16 



apparently more arched. This appearance, however, is due to the 

 prominent dorsal setae, which stand out arching over the dorsum, 

 thus making the animal appear deeper dorso-ventrall}'. A further 

 distinguishing characteristic is the very thin, clear, felty covering 

 over the dorsum. The dorsal setae are very stout dark brown, covered 

 with asperities, and ending more bluntly than they do in any other 

 species of Aphrodita except A. armifera. 



Aphrodita raripillata has a great resemblance to Aphrodita armi- 

 fera (Moore, 1910), and is undoubtedly closely related to it. The 

 chief difference is in the structure of the neurosetae. In Aphrodita 

 armifera the neurosetae of the ventral series are covered with asperi- 

 ties and have a subterminal spur, while in A. raripillata no spur or 

 asperities are seen even under the highest magnification. Moi'eover, 

 Dr. Moore (1910) in his description of A. armifera states that the 

 lateral and the felt fibers of this species are almost colorless, while 

 in A. raripillata they are colorless. 



In a specimen of A. armifera in the collections of the Marine 

 Biological Laboratorj^ of the Scripps Institution at La Jolla, the 

 neurosetae are covered with the asperities and possess a subterminal 

 spur. The lateral and the dorsal fibers, although not conspicuously 

 colored, show a slight tinge of dull green color. 



I feel justified in separating this species on the diiference in the 

 setae, since Dr. Moore (1910), in a similar ease, based the distinction 

 of Aphrodita parva from A. intermedia Mcintosh on the structure of 

 the setae, the only difference between them. Bourne (IS'83), in his dis- 

 cussion of variable and constant characters in the Polynoidae, states 

 that the characteristics of the setae of corresponding segments are 

 constant. Comparing a large number of A. refidgida and A. castanea, 

 I have found that the structure of the setae is a reliable distinguishing 

 characteristic in these species of Aphrodita. 



Description. — The shape of the bodj^ is ovate (pi. 37, figs. 85, 86), 

 obtusely rounded at the anterior end, reaching its maximum width 

 about the tenth segment, decreasing thence towards the posterior end 

 until the last five or six segments form a very narrow caudal end 

 (pi. 37, fig. 85). The dorsum is arched and is covered with a very 

 thin, felty layer over which the golden brown setae arch with their 

 ends nearly meeting over the dorsum near the anterior end. At the 

 posterior end of the body the ends of the notosetae meet or overlap. 

 On the ventral surface (pi. 37, fig. 86) the segmentation is well indi- 

 cated bv transverse ridges. There are thirtv-three segments. The 



