MOLLUSCA OE THE 'CHALLENGER EXPEDITION. 



457 



Mollusca of H.M.S. ' Challenger ' Expedition. — Part X. 

 By the Eev. Eobert Boog Watson, B.A., F.E.S.E., P.L.S., &c. 



[Published by permission of the Lords Commissioners of the Treasury.] 



[Bead June 16, 1881.] 



Earn. Pleurotomid.ze {continued). 



Gren. Pletjrotoma, Lam. 



51. Pleurotoma (Defrancia) hormo- 



phora, n. sp. 



52. P. (D.) chariessa, n. sp. 



53. P. (D.) pachia, n. sp. 



54. P. (D.) pudens, n. sp. 



55. P. (D.) araneosa, n. sp. 



56. P. (D.) streptophora, n. sp. 

 57- P. (D.) circumvoluta, n. sp. 



58. 



Pleurotoma (Defrancia) chyta, 



n. sp. 

 P. (D.) perpauxilla, n. sp. 

 P. (D.) perparva, n. sp. 



61. P. (Daphnella) compsa, n. sp. 



62. P. (D.) aulacoessa, n. sp. 



63. P. (Borsonia) ceroplasta, n. sp. 



64. P. (B.) silicea, n. sp. 



51. Pleurotoma (Defrancia) horhophora, n. sp. (bpfiofopos, 

 collar-girt.) 



St. 23. Mar. 15, 1873. Lat. 18° 24' IS"., long. 63° 28' W. 

 Sombrero Island, St. Thomas, Danish ~W. Indies. 450 fms. 

 Olobigerina-ooze. 



St. 24. March 25, 1873. Lat. 18° 38' 30" N., long. 65° 5' 30" W. 

 North of Culebra Island, St. Thomas, Dan. W. Indies. 390 fms. 

 Coral-mud. 



St. 122. September 10, 1873. Lat. 9° 5' S.,long. 34° 50' W. 

 Pernambuco. 350 fms. Mud. 



Shell. — High and narrow, with no angles anywhere ; porcella- 

 neous to ivory-white, a high conical spire, with sharp reticulately 

 sculptured lip ; the whorls are slightly convex, and have a row 

 of beads round the top of each ; the body-whorl and snout are 

 small, and the base short and contracted. Sculpture. Longitu- 

 dinals — none but excessively oblique, faint, hair-like lines of 

 growth. Spirals — there is a pretty little row of rounded tuber- 

 cles close to the suture at the top of the whorls — about 16 

 in each. The surface is also very finely and superficially 

 microscopically scratched. Colour ivory-white ; but when alive 

 probably porcellaneous, glossy. Spire conical, with scarce any 

 interruption in the profile-lines. Apex consists of 4 conical 

 yellow whorls, rising to a minute tip ; the line of junction between 



linn, journ.— zoology, tol. xt. 36 



