622 THE VOYAGE OF H.M.S. CHALLENGER. 



crowded, on the second and first they are absent. There are besides these very numerous, 

 close-set, rounded, microscopic threads on the lines of growth ; these, as usual, are most 

 distinct on the base. Spirals — there are on each whorl three very narrow rather promi- 

 nent threads, which rise into tubercles in crossing the longitudinal ribs. The highest, 

 which is the strongest, is about two-fifths of the whorl's height below the suture, the 

 costal tubercles on it are sharp and prominent, and it forms a distinct though not strong 

 carina ; on the last whorl the edge of the basal tabulation, which exactly meets the outer 

 lip, forms a fourth thread, and between all the spirals there is a faint trace of one inter- 

 mediate, like a shadow ; on the tabulation of the base there are three or four very feeble 

 and faint rounded threads. Colour glossy, transparent white. Spire very high and 

 narrow, perfectly conical, but having its outlines broken by the strong sutural contractions 

 which constrict the top and bottom of each whorl. Apex small and regularly attenuated, 

 but blunt and quite round, the extreme tip being slightly turned in. Whorls 12^, of 

 very gradual and regular increase ; with a sloping shoulder below the suture, they bulge 

 roundly and contract slightly into the suture below ; the projection of the spiral threads 

 gives the curve of the whorls a slight angulation, which is strongest at the carinal or 

 highest of the three threads ; the base is rounded and scarcely at all projecting. Suture 

 lies in the bottom of a deep and broad angular constriction, and is well marked above by 

 a minute round thread. Mouth small, gibbously oval, slightly pointed above and in front 

 of the pillar. Outer lip thin, advancing very little at its junction with the body, and 

 there a little contracted, slightly patulous in all the rest of its sweep. Pillar very per- 

 pendicular, concave and narrow. Inner lip is carried across the body as a thin glaze ; it 

 spreads out a very little just at the top of the pillar, down which it advances with a 

 very narrow and slightly angulated, but not at all reverted edge. H. 0'36 in. B. O'l. 

 Penultimate whorl, height 0-05. Mouth, height 0-05, breadth 0-048. 



This is a little shell of remarkable beauty. Its generic place lias been very difficult to deter- 

 mine. Its outer Up is a little chipped, which has added to the difficulty. There are none of the 

 microscopic spirals which characterise Turritella. There is no such siphonal canal as would justify 

 its being classed as a Cerithium. The longitudinal sculpture separates it from Mesalia. Mr Edgar 

 A. Smith recommended Fenella, where it is now placed, because nothing more satisfactory suggests 

 itself. Mr A. Adams' diagnosis of the genus (Ann. and Mag. Nat. Hist., 1864, vol. xiii. p. 40 ; 

 Jo urn. de conch., 1868, p. 47, pi. iv. fig. 5) " . . . labro simplici, acuto, non reflexo, incrassato 

 aut varicoso," implies that the outer lip is not reflected, but is either thickened or varicose. In none 

 of the species described is this feature mentioned ; and Mr E. A. Smith writes to me that among the 

 Fenellas of the British Museum, " of which we have several species and many specimens, I do not 

 find any thickening or varix on the labrum." It seems probable, therefore, that Mr Adams' thought 

 was " non reflexo, incrassato nee varicoso," and that " aut " slipped in by accident and transformed 

 his meaning. Still, a slight difficulty remains, since the aperture is not quite "Integra antice," as 

 the old lines of growth indicate, in spite of the chipped lip ; but the indication of an " emargina- 

 tion " is too slight, as is said above, to allow the shell being placed under Cerithiinn. 



