Fam. Seguenzidae. 



Seguenzia Jeffreys. 



I. Seguenzia Melvilli n. sp. PL .XII, fig. 4; PI. XV, fig. 12. 

 Stat. 88. o°34'.6N., II9°8'.5E. 1301 M. Fine grey mud. I Spec. 



Shell moderately large for the genus, conical, scalar, umbilicate, whitish. Whorls about 7, 

 nucleus wanting, upper whorls eroded, lower ones each with three spiral lirae, of which the upper 

 one runs at a little distance from the shallow but distinct suture, which is slightly undulate; 

 from the first liration to the second, the shell is slightly convex, this latter liration is strong, 

 prominent and divides the whorls in two subequal parts ; below this liration the shell is concave 

 towards the basal or peripheral liration, which in the upper whorls, runs just in the suture and 

 in the last one borders the basal surface; these Hrations are slightly spinous; distinct undulating 

 plications run from one to the other of the lower lirae, with the convex side towards the 

 aperture, on the upper part they are directed in an opposite way, being less distinct about 

 halfway the interspace between the upper and median liration ; moreover the whole shell is 

 covered with much weaker striae, having the character of growth-striae and traces of more 

 remote spiral striae. Basal face subconvex, but quite flat in the centre, with a shallow groove 

 between the peripheral keel and the first of the basal lirae, this space is rather smooth, though 

 crossed by plicae running from the peripheral spipes in an oblique direction ; the outermost of 

 the basal lirae, which is not broad, is followed by two similar ones, about as strong as their 

 interstices, the central ones, five in number, increasing in breadth towards the centre, (one of 

 them nearly double) being larger than the interstices, these lirae are connected by small radiating 

 riblets in the interstices; umbilicus bordered by a liration, consisting of a row of subquadrate 

 beads, this umbilicus is pervious, funnelshaped, its wall is radiately striated and has one faint 

 spiral rib. Aperture rounded-subquadrate, its right margin incomplete, its columellar margin 

 curved, with a denticle in the basal part, it is plightly reflected over the umbilicus. Interior 

 nacreous, (the nacreous texture of the inner layers is clearly visible on some of the exterior 

 parts, where the outer layer has been removed by accidents during the youth of the animal). 



Alt. 4'^/,,, lat. sYe; apert. alt. i'/^, lat. 2^^; diameter of umbiHcus about i Mill. 



This species has by its conical shape some resemblance with S. trispinosa Watson, but 

 that species is considerably smaller, with less distinct spines, which have more the character of 

 rounded tubercles, it has smooth interstices, without the conspicuous plications of the new 

 species. The circumstance that the base of the specimens of trispinosa which I could compare is 

 much smoother, seems to give no reliable distinguishing-character, at least Watson ("Challenger"- 

 Gastropoda, p. iio) says: "has some faint spirals". I have named the new species in honour of 

 Mr. J. C. Melvill, who has kindly sent me for comparison all his materials of this genus. 



As to the radula of this species, it is a very small and rather obscure object, and only 

 by teasing it to pieces, I could get an idea of the shape of the teeth, the uncini quite covering 

 the median rows, and crossing even the uncini of the opposite side. The rhachidian or median 

 tooth (R) has a subquadrate basal part, with rounded, convex posterior and less convex lateral 



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