68 "TERRA NOVA" EXPEDITION. 



21. Ton'/liit (Trichoconcha) in!rn!>ilift (Smith). 



Tri<-JiocmieJia iniral!lis, Smith, " Discovery " Gastropoda, p. 6, pi. I, figs. 7-7c (1907). 

 Torcllia (Trichoconcha) mirabilis : Thiele, Deutsche Siidpolar-Bxped., p. 197. 



Station 31 G : 190-250 fathoms. 



Cue adult and two half-grown specimens. The latter have the peristome formed 

 like the full-grown shell, but the spire is more sunken at the apex. Dr. Thiele has 

 suggested that this form approaches T/'cl//ii too closely for generic separation, 

 and that beyond the greater elevation or sunken character of the spire there is little 

 to distinguish the northern and Antarctic genera. 



22. Ni'iicinicliii ri'xtiftt, Smith. PI. I, fig. 8. 



Neoconclia vestita, Smith, " Discovery" Gastropoda, p. 6, pi. I, figs. 11-llc (1907). 



Stations 194, 340, 356 : 50-200 fathoms. 



"It has the appearance of being the young state of a shell that might grow to a 

 considerable size, judging from the large apical whorls." This supposition is now 

 confirmed by the series of adult shells in the present collection. The largest example 

 is 28 mm. in its greater diameter, and 23 in height, Even at this stage the shell 

 is thin and flexible, and consists of four to four and a half volutions, the last being 

 very large and inflated. 



The remarkable, very thick, spongy periostracum is not produced into a sort of 

 coronation, a little below the suture, in any of the specimens, as described in the type, 

 but its growth in oblique, closely packed lines of increment is maintained. It is so 

 thick that the outer margin of the peristome appears to be incrassated, but in fact the 

 shell itself is quite thin. The columella is rather broadly expanded, and is united above 

 to the outer lip by a thin callus. The aperture is of a very pale olivaceous tint 

 inside, but the peristome is bordered within by a reddish brown colour, the extreme 

 edge being paler. The umbilicus is more open in the adult stage than in young 

 specimens. 



This remarkable form is one of the gems of the collection, and does not appear to 

 be circumpolar, since it has not been discovered by any other Antarctic expedition. 



It seems to be fairly constant in its general features, but one specimen exhibits a 

 spiral constriction or sulcus at the upper part of the body-whorl. Another example, 

 somewhat smaller, has four such sulci, marking off five spiral rounded bauds on the 

 body-whorl. 



23. Ni'iiriinr/ui ///.v/,/;//.v, n. sp. PL I, fig. 9. 



Shell globose, thin, narrowly umbilicated, covered with a thick, light, dirty 

 olivaceous, horny periostracum, which is produced into five prominent, equidistant, 

 acute, and delicately fringed keels upon the body-whorl, of which the uppermost 

 revolves up the short spire ; whorls four, very rapidly increasing, the last very large ; 



