GASTROCOPTA. 71 



mm. long, and down to 2x1.05 mm. (PL 17, figs. 13, 14, 15). 

 In these the infraeolumellar tubercle varies from well de- 

 veloped to absent, and the interparietal fold is often wanting. 

 I at first tried to divide the lots into two species, clausa and 

 munita, and it may be that such a division is possible, but I 

 am more inclined to believe the Chatham form a variable, 

 relatively unspecialized population. These small, ill-character- 

 ized clausa with munita-like forms occur together near the 

 shore and also as high as the upper edge of the wooded zone 

 at the border of the grassy zone, on the road to Progreso. 



Gastrocopta thomasseti Pilsbry. PL 14, figs. 5, 6. 



The shell is rimate, thin, cylindric-oblong, the last two 

 whorls almost equal in diameter, those above tapering to a 

 very obtuse summit; pale brown fading to nearly white near 

 the summit, composed of extremely convex whorls, the first 

 two microscopically granulose, narrow riblets beginning then 

 very weakly, on the last two whorls becoming conspicuous, 

 rather widely, unevenly spaced, some ripples between them. 

 There is no crest or ridge behind the outer lip. The aperture 

 is somewhat squarish with rounded angles and a semicircular 

 basal outline, the peristome thin, expanded. The angulo- 

 parietal lamella is more or less distinctly bilobed in a front 

 view, there being usually a slight depression between the sum- 

 mits of the angular and parietal elements. The columellar 

 lamella is rather strong, subhorizontal. The lower-palatal 

 fold is moderately elongate. No other folds are present 

 typically, but in one example a very small upper palatal 

 nodule is developed. 



Length 2.15, diam. above aperture 0.95 mm. ; 5 whorls. 



Length 2.25, diam. above aperture 1.05 mm. ; 5 whorls. 



Kopje on Block Island, Weenen, Natal. Type No. 145474 

 ANSP., paratypes in South African Museum. Collected by 

 Mr. H. P. Thomasset, 1923-1926. 



Gastrocopta thomasseti Pilsbry, Ann. Natal Museum VI, 

 part 2, p. 301, pi. 20, f. 5, 6. 



This species belongs to the little group comprising Gastro- 

 copta klunzingeri (Jickeli), var. senegalensis (v. Maltzan) 



