ii 9 



cylindrical segment and a shorter conical one; they are attached about the middle of the length 

 and not at or near the extremity of the male. The musculature of the sac is strongly developed, 

 the muscles forming parallel hoops along the inner side of the transparent sac. The male genital 

 apparatus is well-developed, the animals being in ripe or nearly ripe condition. The testiculum 

 is heart-shaped and communicates with an oval receptaculum seminis, quite filled up with the 

 thread-like spermatozoa. 



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



Stat. 137. August 3, 1899. Lat. o°23'.8N., Long. I27°29'E. Depth 472 m. Bottom: fine dark 



muddy sand. One large and two smaller specimens. 

 Stat. 212. September 26, 1899. Lat. 5°54'-5S., Long. I20°I9'.2E. Depth 462 m. Bottom: fine 



grey and green mud. One larger specimen. 



Observation. This is without doubt a very characteristic species. The curious shape 

 and structure of the upper latus entitles one fully to say so. The change in shape of the 

 capitulum and of the carina and tergum especially, which appears to take place during growth 

 is, I think, also worthy of mention. I give two figures therefore : one of the largest and one 

 of a younger specimen. 



$j. Scalpellum caudiduui n. sp. PI. IX, fig. 3 and 3^. 



Valves fourteen, not covered by membrane. Carina simply bowed with the umbo at the 

 apex-, its roof flat, very broad, bordered by ridges. L^pper latus pentagonal, apex not produced. 

 Rostrum small, circular. Infra-median latus large with the umbo at the base. Carinal latus 

 triangular, with the umbo at the angle formed by the carinal and basal margins. 



This small species is represented by one specimen only. In many regards it resembles 

 Sc. poculum (pag. 100) and I think it best merely to point out the differences between these 

 two species. 



The lateral and basal margins of the scutum and the short margin separating this 

 valve from the infra-median latus describe together one continuous arch, which is not the case 

 in Sc. poculum. 



The occludent margin of the tergum is distinctly convex, its apex is recurved. 



The carina has the lower part of the roof broader than in Sc. poculum. 



The apex of the upper latus is not produced, not so distinctly produced as in the 

 other species. 



The rostrum is hardly visible. It is a very small circular plate fitting exactly between 

 the upper rostral extremities of the rostral latera. 



The rostral latus has the rostral margin considerably shorter than the lateral margin so 

 that the basal and scutal margins are not nearly parallel (as in Sc. poculum) but distinctly diverging. 



The infra median latus of the present species has a more compressed form. 



The carinal latus is large and has an irregular triangular shape, the lateral and 



upper margins sloping into one another insensibly and the carinal margin forming one straight 



line. The umbo is seated quite at the base where the carinal and basal margins meet at a 



sharp angle. 



119 



