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Show 1879.] CECID.E OF THE ' CHALLENGER' EXPEDITION. 811 The septum is nearly flat, and projects so slightly as to be visible from the side. This species may possibly be only a variety of C. subflavum; but the difference in the septum seems to individualize it. 11. CECUM MICROCYCLOS, n. sp. St. 186. Sept. 8, 1874. Flinders Passage, Cape York. 7 fms. Fourteen specimens. Testa subconica, elongata, arcuata, flavescens, nitidissima, annulis multis parum expressis cincta, aperturam versus paulo dilatata. Apertura haud obliqua, nee contracta, haud marginata ; septo subangulato, submucronato, aliquando bimu-cronato. Length 2 m m . Breadth 0*3 mm. This beautiful species is long in proportion to its breadth; it is conical, rather bent, yellowish, very glossy and nearly opaque. The sculpture consists of numerous small rings, very close-set and slightly prominent. It is sometimes as smooth as C. succineum, from which it differs in its greater length, its more conical form, and the shape of its septum. The mouth is normal in its relation to the axis; it has no marginal ring; and the shell expands towards it regularly without any contraction. The septum is somewhat pointedly subangulated, presenting occasionally two or three very similar protuberances. 12. CECUM ELEGANTISSIMUM, Carp. Feb. 10, 1873. OffTenerife. 70 fms. Six specimens. These specimens present slight differences, but belong unquestionably to this somewhat variable species. 13. CECUM REGULARE, Carp. St. 122. Sept. 10, 1873. Lat. 9° 5' S., long. 34° 50' W . Off Pernambuco. 350 fms. Mud. One specimen. This specimen differs a little from Carpenter's description of C. regulare, but not enough to justify its erection into a separate species. 14. CECUM EXILE, n. sp. St. 172. July 22, 1874. Lat. 20° 58' S., long. 175° 9' W . Tongatabu. 18 fms. Coral. One specimen. Testa minima,paululo subconica, arcuata, vitrea, diaphana, tenuis, nitida, primum annulata, dein transversim striata, annulis minimis vix expressis, aperturam versus paululo inflata. Apertura parum contracta, vix obliqua, marginata, septo vix elevato, submamillato, apice in medio sito. Length 1*5 m m . Breadth 0*3 mm. This pretty little species is somewhat broken at the mouth, but is otherwise perfect. It is slightly conical, crystalline, translucent, glossy and very thin. On the upper part there are rings, which though scarcely expressed are quite distinct under a magnifying |