PROSOBRANCHIATA. 167 



narrow, obscurely channelled behind, and widely notched in front; the outer lip 

 thickened within, thin and sharp at the edge ; inner lip moderately spread over the body- 

 whorl, and presenting at the suture a callus-like thickening, which forms the left side of 

 the posterior canal ; the columella nearly straight, and furnished with two or three not 

 very oblique folds, the front one of which is the most prominent. 



The present species approaches closely to V. geminata, but is much more turbinate, 

 resembling in general form V. spinosa ; and the anterior tubercles are different in their 

 character ; in the present species they are simply an enlargement of the ribs themselves, 

 while in V. geminata, a transverse line runs round the shoulder, and rises into tubercles 

 where it crosses the ribs ; the aperture in V. Forbesii is also narrow and more 

 regularly ovate. This species is found in Hempstead Cliff; and I have dedicated it to 

 the late much lamented Prof. E. Forbes, by whose researches the position of that 

 formation in the tertiary series, so long misunderstood, has been ascertained. 



Size. — Axis, 7-10ths of an inch ; diameter, 4-10ths of an inch. 



No. 106. Voluta calva. Soiverby. Tab. XXI, figs. 6 a, b. 



Voluta calva. Sow. 1850. Dixon's Geol., &c, of Suss., p. 187; t. 7, fig- 28. 



V. testa pyriformi, antice transversim obsolete sulcata, cceterum lavi, ad basin vix 

 emarginatd ; spird brevi, conicd, apice acuto .- anfractibus angulatis, unicd sine spinarum 

 donatis, superne concavis, marginibus anfractu precedenti adpressis : aperturd elongato-ovali ; 

 labro tenui, simplici ; labio parum effuso ; columella subrectd, bis vel ter plicatd. 



Shell pyriform, obscurely ribbed, slightly notched at the base, and presenting 

 several faint, almost obsolete, transverse furrows in front, smooth elsewhere ; spire 

 short, conical, with a small pointed apex : whorls angulated at the shoulder, and 

 crowned with a single row of short, pointed tubercles ; the margins pressed against 

 the spire ; the space between the suture and the row of tubercles concave. The aper- 

 ture of a lengthened oval shape ; outer lip thin, sharp- edged, smooth within ; inner lip 

 very thin and but little spread out ; and the columella furnished with two nearly equal 

 folds in front, and a third very feeble one behind. 



The specimens are generally simply coronated ; but, in some instances, the elevated 

 bases of the tubercles are prolonged into very short, faint ribs. The angulated shoulder 

 and the tubercles distinguish this species from the young shell of V. Selseiensis, with 

 which only it might be confounded. 



Size. — Axis, 1^ inch, nearly; diameter, 7-10ths of an inch. 



Locality. — Bracklesham Bay, where it is somewhat rare. 



