ZooL.-VoL. III.] HOLMES— ON SPHMROMIDS AND DYNAMENE. 303 



is that the head of the male is especially adapted to fit into the under side of 

 the large caudal segment, the 2 parts fitting together very neatly when the 

 animal is rolled up. 



There is a similar adaptation between the head and caudal segment of 

 the female, the head being somewhat differently shaped in relation to the 

 form of the parts against which it abuts. Aside from this, the sexual differ- 

 ences are confined to the posterior portion of the body. In the female the 3 

 tubercles on the convex basal portions of the caudal segment are less prom- 

 inent than in the male, and the posterior emargination much less deep and 

 devoid of lateral teeth. The rami of the uropods are of subequal length and 

 flattened, and considerably shorter than the caudal shield. The tubercles 

 on the first abdominal segment are less prominent, and those on the pos- 

 terior margins of the last thoracic segments may be absent entirely. The 

 whole posterior portion of the body is much less developed in the female 

 than in the male. In immature females the caudal shield is relatively longer 

 than in the adult, the basal portion less tumid, the posterior flattened portion 

 relatively longer, and the tubercle near the apex of the posterior emargina- 

 tion frequently absent. Figure 9 is taken from an immature female collected 

 at Monterey, November, 1895. Larger females taken at San Clemente in 

 the summer of 1894 agree perfectly with Miss Richardson's figure of 

 D. tuberculosa. 



Specimens of both sexes were taken at San Diego, San 

 Pedro, San Clemente Island, and Monterey. Both at San 

 Pedro and at Monterey I have collected numerous specimens 

 from the fronds of kelp. At the latter place they were 

 found in great abundance, and the similarity of habitat and 

 coloration shown by the two forms led to the surmise that 

 they were the two sexes of the same species. This surmise 

 led to the examination of a large number of each of the 

 forms, and it was found that all of the one form were males 

 and all of the other females. 



Dynamene cordata is reported by Miss Richardson from 

 Catalina Island, Monterey, and Popof Island (Aleutian 

 Islands). The female form which Miss Richardson de- 

 scribes as Dynamene tuherculosa is reported from Catalina 

 Island, Gualala, and Bodega Bay, California, and Popof 

 Island, Alaska. I have retained the specific name cordata, 

 rather than tuberculosa, because it was applied to the male 

 form. The fact that the generic name Cilicc^a, as it was 

 founded after Dynamene, cannot be retained in this case, 

 has nothing to do with the validity of the specific name. 



