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Carina! latus elongated pentagonal, narrow, with the umbo about in the centrum 

 of the surface, slightly projecting outwards. 



Sub-carina small; solid, pyramidal, standing out beyond the surface of the carina. 



Peduncle about half the length of the capitulum, rather narrow, narrowest about the 

 middle of its length; surface with minute chitinous scales standing at some distance from one 

 another. In one of the membrane-covered specimens of Station 47'^ the length of the peduncle 

 is more than half the length of the capitulum. 



Size. Length of the capitulum 9,1 mm., of the whole animal 13 mm. in the specimen 

 from Station 2S5; in the largest specimen from Station 47'^ the corresponding dimensions are 

 9 and 13,8 mm. 



C o m p 1 e m e n t a 1 males. Two complemental males were observed in one of the 

 specimens from Station 47'' attached to the surface of that part of the sac or mantle of the 

 hermaphrodite animal which unites the inferior halves of the two scuta. These males are relatively 

 large, the longest diameter of the body being 0,9 mm. Their shape is elongated oval and the 

 body is divided into a larger capitular part and a very short peduncle. The capitulum has six 

 valves: 2 scuta, 2 terga, i carina and i very large rostrum. Fig. 3 of PI. VII has been drawn 

 from the male of this species; it has a great resemblance to the male of Sc\ Peroni and, no 

 doubt, that of several other shallow-water species. 



This species was collected by H. M. S. "Siboga" at two Stations, viz. at: 



Stat. 47''. April 12, 1899. Entrance to Bay of Bima (Sumbawa). Depth 296 m. Bottom: fine 

 sand with mud (coral). Two specimens. One of them was attached to a small 

 stick, to which a piece of coral was also attached. 



Stat. 2S5. January 18, 1900. Lat. 8° 39'.! S., Long. \2-j° \.\ E. Depth 34 m. On the limit between 

 mud and coral, Lithothamnion. (Anchorage south-coast of Timor). One specimen. 



Observations. The present species comes nearest to Sc. Peroni of the known species, 

 e. g. in the number of valves, the shape of the carina and the form (not the size) of the tergum. 

 It differs from it by the absence of the fine spines which cover the membrane in Sc. Peroni., 

 by the valves not being separated by rather wide interspaces of membrane and in the third 

 place by the shape of the latera. 



At first I considered the specimen from Station 285 (PI. VII, Fig. 2) without a distinct 

 membrane as being different from the specimens from Station 47'' (PL V, fig. 15), which are 

 covered with a very conspicuous membrane. Looking at the shape of the capitulum and at the 

 form of the different valves more closely, I became convinced, however, that there was no 

 reason to consider them as specifically distinct. It is true that they were taken at very different 

 depths; but other species also range over depths of rather great difference. Thus, for example, 

 Sc. vulgar e Leach observed in very shallow water and also at a depth of 97 m. For this 

 species Gruvel ^ has described a very characteristic case of polymorphism, corresponding in many 

 regards to what I found in Sc. nncus, viz. that specimens of different localities [? and depths] 

 show difterences in the development of the membrane covering the valves, of the interspaces 

 separating the valves, as also in the grade of calcification, the hairiness of the membrane etc. 



' Gruvel, A., Revision des Cirrhipt-des. Nouvelles .\ixhives du Museum. (IV). IV, 1903, p. 234. 



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