MOLLUSCA OF INDIA. 



383 



hreviter porrecto. Operc. corneum, multis^nrum, externe lurcon- 

 cavum, nudeo centrali interna prominente papillari. 



" Diam. maj. 4, minor 3-25 ; alt. 2-5 mm. 



"■ Eab. Cum A. hebeti in montibus, Khasi, teste W. Theobald, 



""l received two specimens of this species from Mr. Theobald as 

 A. Jiebes, Bens., of which they were supposed to be young shells 

 They, however, prove on closer examination to be fully grown and 

 distinct, the slight swelling in the centre of the constriction con- 

 trasting strongly with the high recurved ridge in A. hebes. This 

 alone would show the present to be a different species, but it is 

 also distinguished by its lower spire, narrower umbilicus, smaller 

 size, and thinner and interrupted peristome, the last character not 

 occurring in any other species of the genus. The well-marked 

 distant costulation of the upper whorls of A. Theobahli is entirely 

 wanting in A. 7iebes. The operculum of the latter does not appear 

 to have been described. A single specimen in my possession is 

 dark horny, indistinctly multispiral, extremely concave in front, 

 and convex almost conical behind and deficient in the central 

 internal boss so prominent in most Alycaji. 



" Although there is a swelling in the centre of the constriction 

 in A. TheobaUi it does not amount to a marked ridge, such as 

 characterizes the typical forms of the section Charax of Mr. Ben- 

 son, e. g. A. stylifer, B. It is consequently not clear whether this 

 species should beclassed with the members of that section, or with 

 those of the typical group. Several species indeed tend to connect 

 these two subdivisions, which more recent discoveries have rendered 

 less distinct than they appeared to be when first described." 



With the now far more numerous known species, it becomes still 

 more difficult to define the limits of Charax, as to character, or 

 to break the genus Alycceus up into sections as Benson and Blan- 

 ford attempted to do. 



This species is variable in size, retaining its principal characters. 

 Thus from the North Khasi Scarp, near Maotherichan Trigono- 

 metrical Station, I obtained 8 specimens (No. 2609 B.M.) far 

 larger than those from Cherra Poonjee. Three of the largest 

 measure 5 mm. in major diameter as against 4 from the last-named 

 locality. It was found at Shillong and Jawai. 



Alyc^us theobaldi, W. Blf., var. solidxjs, G.-A. (Plate CLV. 

 fig. 10.) No. 2560 B.M. 



Locality. Garo Hills {Godwin-Austen). 



Shell depressedly and conoidly globose, openly umbilicated, sohd ; 

 sculpture very distant, strong costulation above, next sutural tube, 

 which is not very long— there are 23 ribs, nearly twice as strong 

 as in typical tlieobaUi, which has about 86, much closer together ; 

 colour pale ochraceous ; spire low ; suture impressed ; whorls 4, 

 rounded, constriction sharp, swelling slightly to the aperture, 

 the distance being greater than in A. theobaldi; aperture nearly 



