262 THE VOYAGE OF H.M.S. CHALLENGER 



This genus differs from Cymhiola of Swainson (the description of which by Adams I have nearly- 

 followed) notably in the texture of the shell which is extremely delicate but on the surface rough, 

 in the suture which is canaliculate, and in the straight pillar which is without teeth but has an 

 abrupt break on the edge. In all the Volutes the last tooth consists of a lamina attached to, or 

 consisting of, the edge of the pillar, the twist on which throws this lamina out as an oblique fold 

 whose abrupt slope looks up the pillar. In Guivillea, on the other hand, the lamina has scarcely a 

 turn at all, and only presents a tooth in consequence of being suddenly arrested and diminished in 

 size ; from this results a tooth whose abrupt slope looks down the pillar. 



In connection with this genus it may be well to recall the Halia of Risso, which has some vague 

 features of superficial resemblance ; but in that genus the columellar tooth, which is almost terminal, 

 results from the extreme and sudden twisting of the pillar. 



I have not given a detailed description of the animal, as the dissection and full representation 

 of it in all its parts is to be supplied elsewhere. 



Guivillea alabastrina, Watson (PI. XV. fig. 2). 



Wyvillea alabastrina, Watson, Prelim. Eeport, pt. 12, Journ. Linn. Soc. Lond., vol. xvi. p. 332. 



Station 147. December 30, 1873. Lat. 46° 16' S., long. 48° 27' E. Between 

 Marion Island and the Croze ts. 1600 fathoms. Diatom ooze. Bottom temperature 34 '2°. 



Animal has an enormous bifid foot, square in front, pointed and high behind ; com- 

 pared to this part the head, mantle, and body are small ; the snout is largish and 

 subcylindrical, above it the great velum extends widely, and is collected into a subconical 

 protuberance at the corners, from which rise the rounded conical tentacles ; no trace of 

 eyes exists. Above the head is the mantle, expanded on the left into the rather short, 

 stumpy, and proboscis-like siphon, which is open below. The reproductive organs, possibly 

 to some extent everted at death, appear like a large tumour on the neck, a considerable 

 way behind the right tentacle. The skin is not tubercled. There is no operculum. 



Shell. — Large, high, thin, white, alabaster-like in texture, with an oval body, a 

 smallish high scalar spire, ending in an irregular, blunt, but pointed, twisted apex ; it has 

 a large oval mouth, a narrow, patulous, not reverted, outer lip, a broad, shallow, truncated 

 canal in front, a broadly spread inner lip, and a straight, toothless, but interrupted pillar. 

 Sculpture : The whole surface is minutely granulated, and has the appearance of havino- 

 been dipped in thin, rather sandy whitewash, and then roughly wiped, especially round the 

 suture. Longitudinals — there are rounded irregular lines of growth, which are generally 

 slight, but all round the mouth-edge a few become somewhat strong. Spirals — there are 

 a few unequal and irregular, broad, scarcely raised threads ; near the suture are some 

 irregular, sharp, quite superficial lines like the marks of rough wiping. Colour alabaster- 

 white, with a roughened, dead, eroded surface. Spire high, rather small, scalar. Apex 

 is blunt, but projects sharply to one side in an excentric and irregular manner. Whorls 



