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Upper latus triangular with the umbo at the apex, this part acuminated fitting into 

 the angle between the scutum and the tergum. Lateral margin concave, carino-lateral margin 

 strongly convex and divided into two unequal parts by the recurved apex of the carinal latus. 



Rostrum (fig. i ^a) very small, elongate, not triangular, laterally covered by the rostral latera. 



Rostral latus quadrangular, low, with the lateral margin only slightly longer than 

 the rostral margin. 



Infra-median latus small, narrow, slightly increasing from the recurved apex to 

 the base. Umbo at the apex. 



Carinal latus with the umbo at the strongly recurved apex. The carinal margin is 

 convex, the upper lateral margin hollowed out. 



Peduncle short, flat cylindrical, only ^/j"' of the length of the capitulum. Scales rather 

 large, placed in five longitudinal rows. 



Size. The total length of the specimen is lo mm., that of the capitulum about 7,5 mm. 



The specimen representing this species in the collection of the "Siboga" was taken at: 



Stat. 251. December 8, 1S99. Lat. 5°28'.4S., Long. 1 32° o'.2 E. Depth 204 m. Bottom: hard 

 coral sand. 



Observations. This species is nearly related to Sr. Iiamulus as also to Sc. rubrtini 

 Hoek which was taken by the "Challenger" near Luzon, at a depth of 180 to 207 m. There 

 are however small differences in the shape of the valves, of the rostrum especially, as also in 

 the size and number of the scales of the peduncle. The description of Sc. rubrum was also 

 given from a single specimen; its capitulum measured only 5 mm. 



17. Scalpelluin sessile n. sp. PI. \TI, fig. 16. 



Valves thirteen, not covered by membrane. Carina short, simply bowed with the umbo 

 at the apex, no fiat roof, but laterally bowed. Upper latus trapeziform. Valves of the lower 

 whorl large. Infra-median latus triangular, with the umbo at the apex and a rather broad basis. 

 Carinal latus very large, pentagonal, with the umbo at the upper extremity. 



This species is represented by four specimens, one being very small. 



The capitulum is rather thick, with the carinal margin much more bowed than the 

 occludent margin. No membrane covers the valves. Whereas the valves of the lower whorl are 

 large, the scutum, tergum and carina are relatively small, the upper latus medium-sized. The 

 valves nearly touch each other; they cannot be said to be separated by chitinous interspaces. 

 The length of the capitulum is twice the breadth it has in the middle, a little above the base 

 of the carina. 



The scutum is about twice as long as broad. The occludent margin is hollowed out 

 in the lower and convex in the upper part; the apex is produced, the tergal margin much longer 

 than the basal margin. The lateral margin is more than half the length of the occludent margin. 



The tergum is triangular; its three margins, the carinal being the longest, are convex. 



The carina is short, simply and rather strongly bowed, with the umbo at the apex. 

 Roof and sides are not separated by ridges, the dorsal surface of the valve being laterally bowed. 



88 



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