102 THE VOYAGE OF H.M.S. CHALLENGER. 



bu1 much projecting scales, placed in rather irregular longitudinal and transverse 

 rows. 



Of the internal structure of the hermaphrodite (female) specimen I am not able to 

 five details. Complemental males are present in numerous specimens, and are of different 

 sizes. They are found attached at the ordinary place, and among them I found one which 

 was still quite in the pupa-stage. I have figured (PI. IX. fig. 10) one of the males, which 

 had the largest size of all, and which maybe safely considered as a full-grown (ripe) male. 

 Its shape is elongate-triangular, its length 1 "5 mm. The body is surrounded by a double 

 wall ; the outermost one represents the mantle, the interior one the true body- wall. 

 The exterior one has anteriorly a slit ; in that part of the body-wall which lies under this 

 slit the male genital organs open. All the specimens have the two angles at the extremity 

 of the shortest side of the triangle produced into conical excrescences, and a globular ex- 

 crescence may be seen, moreover, between the two conical excrescences in the middle of 

 the shortest side. The whole surface is covered by minute hair-like spines, much longer 

 ones being present at the surface of the conical excrescences. The anterior half of the 

 body, where the slit is present, has the spines of a very curious shape, as figured in fig. 10 ; 

 each spine is triangular, the shortest edge being deeply cut in, hence each spine is fur- 

 nished with numerous (three to seven) points. At the surface of each male is attached, 

 moreover, a long and thin chitinous thread, which perhaps serves for the attachment to 

 the scutum of the hermaphrodite specimen. Of the internal organs the male genital 

 apjxaratus seems to be the only one which is left ; it consists in the full-grown specimen of 

 a rather voluminous testis, of a vas deferens, and of a receptaculum seminis. The latter 

 opens with a short duct by the genital pore. 



This species was taken at Station 135, October 18, 1S73; off Tristan da Cunha ; 

 depth, 1000 fathoms; bottom, rock. 



Observations. — The specimen was found attached to a piece of pumice-stone. At about 

 the same place two other species of the genus (Scalpellum elongatum and Scalpellum cari- 

 natum) were taken. 



Scalpellum gigas, n. sp. (PL IV. figs. 1, 2 ; PI. IX. fig. 11). 



Surface of the valves covered by a thin chitinous membrane, wdiich is not villous. 

 \ alves fourteen. Carina simply bowed, rather massive, with the umbo at the apex, and a 

 laterally slightly convex roof and two flat sides forming a slightly obtuse angle with the 

 roof. Upper latus quadrangular. Carinal latus very high. Peduncle about half as long 

 as the capitulum. 



This species is no doubt very nearly related to Scalpellum darwinii, and I was long 

 in doubt as to whether I should regard them as distinct or not. The smoothness 



