15l8.] N. Annandale : Molluscs of the Inle Lake. 127 



viridis, fasciis latis castaneis 2 in anfractibus superis, 3 in ultimo ornata. 8piia conica 

 apice acuto, nigrofusco ; sutura clistincta pallidius marginata, intcrdum subirregulariter 

 impressa. Anfractus 7 regularitcr accrescentes, supri convexi, laeves, inferi ad suturam 

 planati et cingulis spiralibus parum prominentibus distantibus varie cingulati, ultimus 

 interdum subrotundatus, interduin distincte angulatus, postice spirae altitudinem 

 superans, antice vix descendens. Apertura obliqua, irregulariter ovata, faucibus fusces- 

 centibiis fasciis translucentibus ; peristoma callo crasso fuscescente continuum, margine 

 extcrno recto vel (? in spec, adultioribus) leviter expanse, columellari usque ultra basin 

 valde calloso, incrassato, dilatato, interdum saturate fusco, appresso, umbilicum omnino 

 claudente. 



Alt. 32, diam. max,. 21-5, alt. apert obi. 18, diam. cum perist. 16 mm. 



The operculum and radular teeth are figured on pi. XVIII, figs. 1, 2. 

 The teeth are rather paler in colour than those of T. theohaldi. 



All authors who have referred to and figured the shell have recog- 

 nized its variability. Theobald in his original description named two 

 varieties {fasciata and carinata), while Nevill gave the typical form the 

 name var. concolor. These varieties, however, as their authors re- 

 cognized, have no constant character and are linked together by inter- 

 mediate phases. They represent no more than individual variation, 

 and shells belonging to all of them, and to intermediate phases, occur 

 together under identical conditions. The species also exhibits a cer- 

 tain racial variation correlated with environment. Theobald's speci- 

 mens, of which some are preserved in the Indian Museum, were from 

 the Upper Sal ween in the eastern part of the Shan States. Unfor- 

 tunately we have no information as to the type of environment in which 

 they were found. They are of relatively small size, and of somewhat 

 elongate form, though the body-whorl is usually globose or sub-globose. 

 We found in small sluggish streams on the He-Ho plain a very similar 

 race, exhibiting almost the same variation in shell-characters, but 

 including individuals of somewhat larger size. In ponds and swamps 

 in the Inle basin there lives a slightly different race, with the shell of 

 somewhat smaller size, a little more globose and never with the sculp- 

 ture so well-developed as in the var. carinata. The difEerences in both 

 races are beyond the range of exact statistics or of mensuration, depend- 

 ing as they do mainly on difTerences in outline and details of the pro- 

 minences on the shell and of colouration. I will, however, discuss them 

 as precisely as possible later (p. 160). 



The form that I have described in this paper as Taia intermedia 

 (p. 128) is hardly more than a standardized type of T. naticoides var. 

 carinata, but the fact that it is standardized is of great interest and 

 seems to warrant its reception of a differential name. I have already 

 alluded to the awkwardness inherent in a trinomial nomenclature when 

 large numbers of allied forms have to be considered, and here the dijfi- 

 culty is increased because intermedia is to all aj^pearance a fairly con- 

 stant form derived from and but little difierentiated from a most variable 

 species. To adopt for it Theobald's name carinata might be legitimate 

 on purely technical grounds, but this would conceal its true relation 

 to T. naticoides. Moreover, its identity with the var. carinata of 

 that species, though closely approximate, is not absolute (see figs. 3-6, 

 pi. xvi). 



The only locality records for T. naticoides, apart from Theobald's, 

 are Kobelt's : — Meungyaw in Upper Burma and Lashio in the Northern 

 Shan States. 



