218 Transactions. — Geology. 



which it may be distinguished by the longitudinal and spiral 

 sculpture being much less developed, giving it a more smooth 

 appearance. 



Pleurotoma albula, Hutton, var. subalbula, n. var. 



Plate XX., fig. 2. 



Shell small, fusiform ; body longer than the spire ; 

 whorls 8, protoconch two whorls, smooth and polished, the 

 third usually irregular growth-lines only ; the two succeed- 

 ing whorls with two spiral ribs, the anterior somewhat the 

 stronger, and one or two spiral threads ; on the next, or 

 antepenultimate, a sutural thread gradually strengthens, form- 

 ing a third rib, which on the penultimate equals in size the 

 posterior rib ; in addition to these, there are two or three 

 spiral threads between the subcentral and posterior rib, and a 

 like number between the latter and suture ; on the body- 

 whorl are three spiral ribs in front of the aperture, usually 

 less distinct as they approach the outer lip, and with one oV 

 two threads in the interspaces ; anterior to this are ten or 

 eleven small spirals, somewhat irregular in size ; above the 

 sinus are seven or eight threads, two of which are slightly 

 stronger, and in some examples form small ribs ; the whorls 

 transversely striate with growth-lines, oblique on the sinus 

 area ; aperture narrow, slightly contracted below ; columella 

 straight, somewhat callused, canal short and slightly curved, 

 outer lip thin, sinus shallow. Length, 12 mm. ; breadth, 

 5 mm. 



Type, Wanganui Museum. 



Locality. — Blue-clay cliffs, west of Wanganui Heads. 



Compared with a typical example of albula, this shell 

 differs in the most prominent rib not being central on the 

 spire-whorls, but nearer to the anterior ends, the area above 

 the sinus wider, the columella stronger, canal less produced, 

 and by the shell in general having a stouter aspect. This and 

 the preceding species should probably be referred to section 

 Surcula. 



Clathurella sinclairii, Smith. Plate XX., fig. 7. 

 Smith, Ann. and Mag. Nat. Hist., 1884, vol. xiv., p. 320; 



Tryon, Man. Conch. (1), vol. vi., p. 283, pi. xxxiv., fig. 91. 



To determine this species from other nearly allied fossil 

 forms IS not always an easy matter. The example chosen for 

 illustration is recent, and a brief description of it may not be 

 out of place. 



Shell whitish, with a nari'ow brown band near the pos- 

 terior end of whorls, and a wider band towards the an- 

 terior end of body-whorl (some examples without colour- 

 bands) ; whorls 6-6i, apical whorl smooth, the others trans- 



