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the height of the moveable tergum and scutum and the numerous ridges which serve for the 

 articulation of these valves. 



3. Verruca cassis n. sp. PI. XI, fig. 1—6. PI. XII, fig. 7—8. PI. XIII, fig. 8—10. 



Shell not depressed, moveable valves nearly perpendicular to the surface of attachment. 

 Moveable tergum with five longitudinal ridges, moveable scutum also with five ridges, the 

 fifth extending along the middle articular ridge on the side of the occludent margin of the 

 valve. Carina with the apex rounded at the tip and slightly produced only, much smaller than 

 the rostrum. Apex of rostrum rounded, not produced. Carina and rostrum articulating with 

 4 to 5 teeth which diminish in size towards the basal margin. Fixed tergum and scutum articu- 

 lating: with the aid of two narrow and somewhat indistinct ridges. 



Several specimens of a Verruca were collected at different stations in the Malay Archi- 

 pelago, at depths varying from 800 to 1600 m., and, although differing in certain characters from 

 each other, must all be considered as belonging to one and the same species. The differences 

 must be attributed, I think, partly to differences in age, partly to differences in the surface 

 of attachment, which is very narrow for specimens attached to sponge-needles and broader for 

 those attached to sterns of a different nature. 



The colour of the shell is white in young specimens and dirty-yellowish in older; traces 

 of a chitinous membrane are here and there visible. The growth-ridges are not very distinct 

 on the rostrum and carina but can distinctly be made out on the moveable valves as well as 

 on the fixed scutum and tergum. The moveable valves are relatively large, the rostrum rather 

 bulky and broad ; the broken line of articulation between rostrum and carina is not near the 

 middle of the front side of the shell but towards its carinal side (PI. XII, fig. 7 and 8). 



The moveable scutum (PI. XI, fig. 1) is not very small, its area equalling about 

 two-thirds of that of the moveable tergum. Its shape is triangular, the occludent margin strongly 

 curved, the basal margin almost at right angles to the tergal margin and more than half 

 as long as that margin. The tergal margin shows five rather blunt excrescences or teeth: the 

 apex of the valve being the first, the extremity of the axial ridge the fifth of these teeth ; the 

 basal margin has two such blunt excrescences, one at the extremity of the axial ridge and one 

 at the extremity of the fifth ridge which runs along the axial one. Of these ridges the first is short, 

 narrow and indistinct: only visible when the valve is isolated; the second is much broader and 

 extends to about half the length of the tergal margin ; the third is slightly narrower than the 

 second, distinctly curved, extending to within a short distance from the extremity of the fourth 

 or axial ridge. This axial ridge is very prominent, curved and grows broader from the apex 

 towards the basi-tergal corner, where it projects freely. The fifth is about as broad and strong 

 as the axial ridge, but its extremity can hardly be said to project freely, though forming a 

 little excrescence on the basal margin of the valve. This fifth ridge. is hardly visible in the 

 smaller, no doubt younger, specimen. The part of the valve which is enclosed between the 

 last (fifth) articular ridge and the occludent margin is relatively narrow and shows, especially 

 in the inferior part, distinct ridges of growth which run parallel to the basal margin. 



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