/ / 



Rostrum (fig. 5a) small, triangular, totally covered by thick chitinous membrane. 



The upper latus is pentagonal with the sides of unequal length: the basal margin 

 separating it from the infra-median latus is the shortest, the tergal margin the longest. The 

 umbo is seated at a little distance from the apex. 



The rostral latus is trapeziform : the scutal and basal margins run parallel, the lateral 

 margin is convex and the rostral margin also slightly arched. The upper halves of the two 

 rostral margins limit a small triangular space which is occupied by the rostrum. 



The infra- median latus has a triangular basal part and an elongated triangular 

 upper part. Where the two parts unite the umbo is seated. The lateral margin of this valve 

 can not well be made out; most probably, it is slightly concave. 



The carinal latus is quadrangular. The carinal margin is hollowed out, the umbo is 

 seated at a little distance from the base. The basal margin is short, the lateral margin feebly 

 arched, the upper margin short and straight. 



The peduncle is cylindrical. The scales are narrow, laterally more strongly developed. 

 They are placed on six longitudinal rows: one rostral, one carinal and on both sides two lateral 

 rows. In the specimen figured there are about 9 scales in each longitudinal row. 



Size. The specimen figured is the largest of the three. Its total length was 45 mm., that 

 of its capitulum 27 mm. One of the specimens was found attached to a rounded piece of very 

 porous stone, most probabl}- pumice-stone, the two others to a specimen of i>. »ioluccanum, 

 the only one collected during the cruise of H. M. S. "Siboga". 



The study of the structure of the female animal contained within the capitulum has 

 yielded the following results: 



Mouth bullate, same shape as in the other nearly related species. Second maxilla 

 with the openings giving entrance to the body cavity at the end of long and flat tubular projections. 



The first cirrus has both branches short, broad, flattened; the anterior branch 

 considerably broader than the posterior. The second cirrus is placed at a little distance 

 from the first with longer, cylindrical rami; the cirri of the four last pairs have very lono- and 

 strongly curled rami. 



The caudal appendages have six segments, the last one is abruptly cut off in a 

 transverse direction and bears numerous hairs on the extremity. 



No trace of a penis; I consider the large animals unisexual and female, the males as 

 dwarf-males. 



Four d w a r f - m a 1 e s were found in the left pouch formed by a duplicature of the sac 

 or mantle, at the inner side of the scutum in front of the adductor muscle. There are several 

 in the right pouch also, but I could not count them without loosening the pouch from the 

 scutum. The size of the males is i mm. in length and about 0,6 mm. in breadth; shape oval. 

 Opening giving entrance to the sac at the capitular pole. The prehensile antennae are attached 

 to the little body about the middle of its length. The whole surface bears minute hairs; they 

 are longer and stouter, however, at the extremity opposite the capitular pole. A few longer, 

 but very delicate hairs form a tuft, one at each side of the mantle- or sac-opening. The male 

 corresponds on the whole in shape and structure with that of Sc. javanicjim, Sc. airioswii etc. 



77 



