EUTHYEXIA. 27 



anteriorly, in a line with its upper extremity, a minute, hori- 

 zontally elongated denticle, and, in a line with its base, a larger 

 denticle, elongated obliquely. Above the periphery occurs, in 

 addition, a small, horizontal denticle, and below the umbilical 

 nngulation a short horizontal fold. The two specimens figured 

 lire in Mr. Ponsonby's collection. That shown in fig. 5 b is not 

 quite mature, the newly-formed palatal armature consisting of 

 only one horizontal and two vertical denticles. The late 

 Col. Beddome's collection contains a large series of this species 

 from the Tinnevelly Hills ; of these, nine full-grown specimens 

 possess only one set of denticles ; five not quite full-grown 

 specimens are each provided with two sets of denticles, the older 

 being complete, while the newly-formed sets consist of one, two, 

 or three denticles ; four immature specimens have only one set of 

 denticles ; ten other immature shells possess each two sets of 

 denticles. Of the latter, three have the older set complete and the 

 newer set partly formed, five have the older set incomplete (partly 

 absorbed) and the new set complete; while, finally, the two 

 remaining specimens have both sets complete. It may, therefore, 

 be safely inferred that the older set does not become absorbed 

 until the new set is completed. In a few instances I have 

 observed that the two lower anterior denticles have become 

 fused. 



45. Ruthvenia clathratuloides. Gude. 



Plectopylis clathratiiloides, Gude, Science Gossip, x. s. iii, 1897, p. 332, 



fig. 44. 



Plectopylis (Sykesia) clathratuloides, Gude, op. cit. vi, 1899, p. 149. 

 Sykesia clathratuloides, Godwin- Austen, Moll. India, ii, 1907, p. 199. 



Original description : " Shell depressed conical, moderately 

 umbilicated, pale corneous, translucent, finely and regularly pli- 

 cated by raised ribs above, finely and closely ribbed and a little 

 shining below ; whorls 5| slowly increasing, slightly convex, 

 suture impressed. Periphery with an acute compressed keel, 

 above which revolve two raised spiral ridges, the lower provided 

 with a fringe of coarse hairs. Aperture subquadrate ; peristome 

 simple, a little thickened. Umbilicus deep and moderately wide. 

 Parietal armature, one strong, vertical, simple plate. Palatal 

 armature in two series ; upper series with one posterior, vertical, 

 conical tooth and one minute anterior denticle ; lower series, with 

 one posterior, vertical tooth and a small anterior denticle ; in 

 addition, one elongated horizontal fold below the umbilical 

 angulation and a small fold above the peripheral angulation. 



" Diam. maj. (5, min. 5'5. ; alt. 3-5 mm." (Gude.) 



Hob. India : Auamullay Hills ; Madura (Beddome). 



The present species differs from R. clathratula in being more 

 elevated, in having a narrower umbilicus, and in being less shining 

 and more tumid below, while from Ii. retifera it differs in the less 

 elevated spire and the wider umbilicus ; it is, in fact, intermediate 



