MOLLUSCA OP THE { CHALLENGES' EXPEDITION. 123 



(which, as in the case of these two species, is mammillate and dis- 

 tinct from the acute form of C. reticulatum, della Chiaje) is more 

 oblique than it is in these. 



The last four species, C. cylindricum, C. abruptum, C. delicatum, 

 and C. aedonium, I keep here together. They have undeniably the 

 deep oblique siphonal cut on the base toward the point of the 

 pillar which is a very marked feature in Cerithiopsis ; but the 

 form of the canal is very variable in all the group, and the elon- 

 gated and sculptured apex, which is a still more characteristic 

 feature of Cerithiopsis, is wanting ; and thus, in the absence of the 

 animal and operculum, I prefer classing them as above with Bit- 

 tiwn. I confess, however, that on both of these grounds Cerithi- 

 opsis costulata, Moll., seems quite as doubtfully entitled to rank 

 as a Cerithiopsis. 



Litiopa. 



LlTIOPA (?) LIMKiEIEOEMIS, n. sp. 



St. 144 c. Dec. 27, 1873. Lat. 46° 48' S., long. 37° 49' 30" E. 

 Priuce Edward Islands, between Cape of Good Hope and Ker- 

 guelen. 50-150 fms. 



Shell. — Obliquely ovate, thin, smooth, whitish, horny, with a 

 slight, almost covered umbilical chink. Sculpture. There are many 

 faint oblique lines of growth, but Hone other of any kind. Colour 

 whitish, horny. Spire conical, slightly scalar. Apex small, but 

 bluntly rounded, and neither sharp nor sculptured. Whorls 3|, 

 of regular, but rather rapid increase, a little tumid, and convex, 

 but flattened, in a line parallel to the axis ; the base is tumid 

 and somewhat produced. Suture strong, impressed, and almost 

 a little canaliculate. Mouth perpendicular, oval, not at all 

 pointed. Outer lip thin, a little incurved above, slightly patulous 

 in front, and projecting beyond the pillar, between which projec- 

 tion and the pillar it retreats as a slight and open sinus. Pillar 

 perpendicular, a little hollowed, twisted, and truncate. Inner 

 lip spread out over the body- whorl and behind the pillar, so as to 

 conceal and almost close tbe umbilicus, below which it crosses, 

 with an oblique thin edge, to join the front of the pillar below its 

 twisted truncation. Umbilicus not small in itself, but almost 

 quite hidden. H. 0-089. B. 006, least 0-047. Penultimate 

 whorl, height 0-02. Mouth, length 0'052, breadth 0039. 



This is another of the unsatisfactory cases where a species is 

 classed under a genus for want of a better. The texture of the 

 shell is somewhat like that of Litiopa, but it utterly wants the 



