Spirotropis.] GASTROPODA. 483 



Genus 3. SPIROTROPIS. Sars, 1878. 



Spirotropis, Sars, Moll. Norv., 1878, 242. Type : Pleurotoma bicarinata, 

 Bivona. 



The teeth of the radula are very distinct, the formula being 

 l + l + l+l-l-l ; the central tooth transverse, triangular, with a 

 median and several denticles on each side, the lateral teeth long, 

 subulate. 



Shell turriculate, with a high and gradated spire ; protoconch 

 paucispiral, globular, the nucleus obtuse ; whorls smooth, carinated 

 at the middle, excavated above, the body-whorl convex, lightly con- 

 tracted below ; aperture pyriform, with a short wide canal, not 

 emarginate at its base ; outer lip arcuate, thin, with a rather broad 

 and deep sinus near the suture ; inner lip thin and narrow. Oper- 

 culum normal. 



Only a few species are known. The type occurs from the Mediter- 

 ranean Sea to Norway, in deep water. 



Fossil in the Miocene and Pliocene of Europe. 



1. Spirotropis bulbacea, Watson, 1881. Plate 21, fig. 10. 



Pleurotoma (Drillia) bulbacea, Wats., J.L.S., xv, 1881, 418. Pleurotoma 

 (Spirotropis) bulbacea, Wats., Chall. Rep., xv, 325, pi. 25, f. 9. Drillia 

 bulbacea, Wats. : Button, P.L.S. N.S.W., x, 116. Spirotropis bulbacea, 

 Wats., Index, 70. 



Shell broadish, conical, sharply keeled, strong, porcellanous, with 

 a shortish contracted base, a short canal, short narrow ribs, spiral 

 threads, and a bulbous apex. Sculpture : Axials below the sinus- 

 area arise ribs, slightly tubercled at the top, straight, narrow, and 

 parted by shallow furrows about twice their breadth ; they become 

 feeble toward the lower suture ; on the last whorl they do not con- 

 tinue to the base ; there are 11 on the last two whorls ; on the first 

 infraembryonic whorl there are about 17, crowded, sharp, and oblique ; 

 the lines of growth are numerous and unequal, in the sinus-area they 

 are sharp and delicate, on the rest of the shell coarse and puckered. 

 Spirals marginating the suture below as a narrow band ; below 

 this the sinus-area is very finely scratched, this is continued less dis- 

 tinctly on the rest of the surface. The projection of the top of the 

 ribs forms a sharp keel. The rib-area is crossed by 5 coarsish threads, 

 which rise into small tubercles on the ribs, 1 or 2 smaller threads come 

 in between the lines of these spirals ; they are also found on the base, 

 though less distinct. Colour dull porcellanous-white. Spire rather 

 short, conical, slightly scalar, about the same height as the aperture. 

 Protoconch of 2 smooth convex whorls, with a deep suture. Whorls 6J, 

 short, rather rapidly increasing, concavely shouldered, slightly con- 

 tracted towards the lower suture ; base somewhat narrowed. Suture 

 coarse, slightly impressed, margined below. Aperture narrowly oval, 

 pointed above, with an oblique short rather open and gradually con- 

 tracted canal below, not emarginate at its base. Outer lip depressed 



16* 



