62 



Caudal appendages triangular, uni-articulate, small; a tuft of about half a dozen 



delicate hairs at the extremity. 



Penis rather short, reaching to the extremity of the fifth segment of the last pair 

 of cirri; its basal part broad with only a few scattered hairs, the terminal part of about the 

 same leno-th as the basal part, cylindrical, rather narrow, indistincdy ringed. It bears very 

 delicate hairs, which are irregularly distributed over the surface and a rather dense tuft of 

 hairs at the extremity. 



The mantle-cavity of the hermaphrodite animal investigated more in detail contained six 

 rather large and nearly globular eggs. The greatest diameter of the eggs is 0,34 mm., the 

 shortest 0,28 mm. They contained larvae in the Nauplius-stage, some of the larvae had partly 

 shed off the exuviae. 



The male of this species is a true complemental male. I found two of them in the 

 one, one in the other pouch of the hermaphrodite specimen. In fig. 10 the place occupied by 

 this pouch is indicated as a little swelling (d). The male is figured PI. 5, fig. i i ; its size is 

 0,35 mm. X 0,25 mm. It has six valves: two scuta, two terga, a carina and a rostrum, the 

 general shape of which can be seen from the figure. The scutum is the largest, the rostrum 

 is much broader than the carina. The tergum has an irregular shape and is divided into two 

 parts: a larger somewhat excavated at the apex and a very small one at the place of the 

 primordial valve. Shape and position of the valves resemble the corresponding parts in the male 

 of Sc. Peroni and Sc. villosuDi as described by Darwin. But the males of the present species 

 have no narrow peduncle, the capitulum going over quite ijisensibly into the short and flattened 

 part to which the prehensile antennae are attached. The membrane connecting the valves is 

 very slightly rough, but it does not bear distinct hairs. Extremely minute hairs seem to be 

 planted on the surface near the pedunculai- pole only. The musculature of the peduncular part 

 of the sac is strongly developed. 



The structure of the little body within the sac corresponds in general but in reduced 

 condition with that of the hermaphrodite animal as also with that of the males of the nearly 

 related species Sc. villostnn and Sc. Peroni. It has verj- large e)es situated in the median line, 

 beneath, or rather in front of the strongly developed adductor muscle. The mouth is slightly 

 bullate; the cirri have but few segments (four in the first, five in the second pair). The penis 

 is short, cylindrical, rounded at the extremity, where it bears a few curled hairs or bristles. 



This species was collected during the cruise of H. M. S. "Siboga" at: 



Stat. 274. December 26, 1899. Lat. 5°28'.2S., Long. i34°53'.9E. Depth 57 m. Bottom: sand 

 and shells, stones. 6 specimens. 



Observations. This is a very curious species. It belongs to the same group as Sc. 

 villosum (Leach) and Sc. trispiiios-iiiii mihi as is shown at once by the shape of the carina. 

 It has one pair more latera, however, than one of these two species and the general shape of 

 the capitulum is more like a normal Scalpclbtiii in consequence. Like Sc. villosuvi and irispi- 

 nosum it comes near to Pollicipes, especially P. serttis and this is particularly the case with 

 regard to the shape of the valves of the lower whorl. 



One of the specimens shows this relation in a still more conspicuous way and I have 



