1879.] C^CID^E OF THE ' CHALLENGER' EXPEDITION. 807 



tissime et irregulariter transversim striata; apicem versus 

 paululo tumidula. Apertura obliqua, haud maryinata. 



Length 2*3 mm. Breadth 0"2 mm. 



The apex of this specimen has been broken and restored ; so that 

 its original form is somewhat obliterated. The species presents the 

 usual slight swelling at the beginning of the curve, a little way from 

 the apex. It has three curvatures. The aperture is oblique. From P. 

 asturiana (see 'Les Fonds de la Mer,' vol. i. pp. 174 and 218, pi. xxix. 

 fig. 7) it differs in that the shell here is shorter, the curves stronger, 

 while the annular striations are much finer and are differently ar- 

 ranged. Its form distinguishes it fromP. cornucopia ('Les Fonds,'&c. 

 vol. i. pp. 122, 174, 218. pi. xv. figs. 7-9). The absence of the charac- 

 teristic apex is a feature noticeable here, as well as in some specimens 

 of P. asturiana which yet present all the other characteristics of 

 the genus. In a shell so sharp at the point a fractured apex is not 

 wonderful ; it doubtless occurs through accident ; and the injury is 

 repaired, and the ^traces of it concealed, by deposition of shelly 

 matter. 



s* . 2. Strebloceras subannulattjm, n. sp. 

 ^r : July 1875. Reefs off Honolulu. 40 fms. Three specimens. 



Testa minuta, bicurvata, vitrea, diaphana, nitida ; nucleo spira/i, 

 obliquo ; anfractibus duobus ; postea testa tubularia, latitudine 

 accrescens, curvam duplicem sequens, transversim subannulata, 

 annulis latis, minutissime expressis, subacutis, late separatis, 

 Apertura obliqua. 

 Length 3 mm. Breadth 0'5 mm. 



These three specimens are the first living representatives of the 

 genus ; and that they really belong to it is obvious, since the nucleus 

 exhibits two or two and a half whorls and is placed at the side, 

 not in the central plane of the shell — the position occupied by the 

 nucleus in Ccecum with as many whorls, and in Parastrophia with 

 only half a whorl ; and this is a distinction of great importance. 

 Below the nucleus the shell increases steadily in breadth, and as it 

 lengthens takes a curve in two planes. The shell is vitreous, trans- 

 lucent, glossy, and thin, ornamented by broad, remote, transverse 

 slightly sharp undulations, which can hardly be reckoned rings, 

 "being so faint as only to be visible under the microscope. This 

 ornamentation, slight as it is, is very characteristic. The mouth is 

 oblique, with the obliquity turned towards the plane of the apex of 

 the nucleus. This is a feature of some importance in the family of 

 Caecidae, the direction of the oblique mouth being constant in the 

 well-known genera Ccecum and Meioceras ; and the same may be 

 affirmed of Parastrophia. 



Watsonia, nov. gen. 

 Testa probabiliter primum nucleosa, postea tubularia, decollata, vix 

 bicurvata, conica ; apertura orbicularis, valde obliqua, valide 

 circumdata. 

 The three specimens here under consideration have all the 

 Proc. Zool. Soc— 1879, No. LII. 52 



