228 ZONITID^E. 



Island. Specimens have also been received from the Andamans 

 (var. cadelli, Nev. MS.) and the Nicobars. 



The shell in this species varies much ; some are thin and horny 

 with the spiral ribbing almost obsolete, in other cases the shells 

 are thicker and the ribbing strong throughout. From S. infula it 

 is distinguished by more open perforation and by lower spire. It 

 is also, as a rule, much larger, with more numerous whorls. 



Animal dull whitish, ridge of posterior part of foot grey, mantle- 

 lobes light or sometimes pinkish grey, inner part of mantle with 

 spots and stripes of dark pigment. The dart-sac is present and 

 consists of a strong, tough, twisted tube ; spermatheca club-shaped, 

 swollen at the end, then narrowing to a tube, and again swollen 

 near the orifice ; vas defer ens short and thin, expanding before 

 joining the penis, which is connected with the retractor muscle by 

 a long caecum. Jaw semicircular, scarcely projecting in the middle 

 of the concave edge. Teeth of radula 200 .2.1.2. 200, in about 

 100 rows, middle tooth long, tricuspid ? (too many cusps are re- 

 presented in Stoliezka'*s figure ; he probably made the drawing by 

 eye and not with a sufficiently powerful microscope), the next two 

 broader, but passing into the narrower admedian, having one cusp 

 in the outer edge ; the marginals are serrated on the outer edge. 



[338. Sitala vulcania, sp. n. 



Locality. Narkondam Island, Bay of Bengal (G. Rogers, Oct. 

 1904). 



It is interesting to find this genus on this small volcanic cone, 

 lying some 85 miles east of the North Andaman Island. I have 

 compared it with S. attegia, var. cadelli, Nev. MS., from the 

 S. Andamans. There is considerable difference in form ; the 

 Narkondam shell is more sharply keeled than cadelli or typical 

 attegia, and the whorls are more convex, the spire less high. 

 Considerable difference is found in the sculpture : in the Andaman 

 S. cadelli there is very fine irregular striation on the last whorl, 

 with very regular distinct liration on the apical whorls ; in the 

 other, vulcania, there is coarse irregular striation on the last 

 whorl, indistinct liration on the apical whorls, with slight indica- 

 tion of same on the basal side. The animal was in a very good 

 state of preservation. Foot divided, the usual peripodial grooves, 

 and broad fringe below. Head darkish grey, also keel of foot. 

 There is a very minute right shell-lobe. 



The generative organs agree very well with Stoliczka's description 

 and figure of Sitala infula, Bs. The penis and spermatheca are 

 exactly the same, and the amatorial organ is absent, as in that 

 species. 



The radula I was fortunate in extracting complete ; it is very 

 broad, having a large number of teeth in one row, the formula 

 being 



210 . 2 . 1 . 2 . 210 

 212 . 1 . 212 



