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Show 1879.] CECIDiE OF THE ' CHALLENGER' EXPEDITION. 809 seen with a septum of this character ; and, misled by this feature, at first considered it to be a specimen of C. r ever sum, Carp.; but that species belongs to his group Fartulum, with which the specimen in hand has nothing to do. I believe it to be a new species. 5. CECUM ATTENUATUM, n. sp. Sept. 8, 1874. Flinders Passage, Cape York. 7 fms. Nine specimens. Testa, quoad genus, mediocris, conica, arcuata, elongata, alba, nitida, subopaca, annulis numerosis crebris, haud seu vix cincta, aperturam versus paululo latior vel dilatata. vix obliqua, haud marginata, parum contracta, septo mamillato-ungulato, margine laterali bicurvato, dorsali gibboso. Length 1*8 m m. Breadth 0*4 mm. A very curious species, very small, conical, curved, long in proportion to its breadth, slightly glossy, opaque. It looks smooth ; but under a lens it appears ornamented with numerous close-set, scarcely projecting rings. Towards the mouth the shell broadens a little and then contracts, thus forming a peristome which is slightly oblique and has no ledge. The septum is enormous, and in form is at once mamillated and ungulated. Its dorsal protuberance or hump, when looked at from behind, rises in an equable curve from either side. 6. CECUM SEPIMENTUM, de Folin. July 1875. Reefs off Honolulu, 40 fathoms. Many specimens. Var. ARCUATA, de Folin. St. 172. July 22, 1874. Lat. 20° 58' S., long. 175° 9' E. Tongatabu. 18 fms. Coral. Surf. temp. 75° F. One specimen. Sept. 28, 1875. Tahiti Harbour. 20 fms. Two specimens. De Folin, Les fonds de la mer, vol. i. p. 84, pi. vi. fig. 7. A species described from specimens dredged at Mauritius. The numerous specimens from Honolulu are quite of the typical form. The var. arcuata is shorter and more bent. The specimen from Tonga-tabu is somewhat broader and has thicker rings than those from Tahiti. 7. CECUM, n. sp. July 1875. Reefs off Honolulu. 40 fms. One broken specimen. Probably a third of the shell is broken away. It is ornamented with strong and pretty regular rounded transverse rings, which are parted by hollows equally broad and rounded with the rings. The septum is regularly and hemispherically mamillated with a coarsely tubercled surface. It seems to be a new species. 8. CECUM CHINENSE, de Folin. St. 186. Sept. 8, 1874. Lat. 10° 30' S., long. 142° 18' E. Wednesday Island, Cape York. 8 fms. Coral-sand. Surf. temp. 77°'- 2 F. Two specimens. De Folin, ' Les Fonds de la Mer,' vol. i. p. 80, pi ix. figs. 3, 4. 52* |