AMPIllDROMfS, GROUP XVIII. 



Amphidromus kobelti Rolle (Nachrbl. il. D. Mulak. Ges., April, 

 1893, p. 34) is considered a synomyn by Fulton, but from his re- 

 mark on its coloration it is evident that he had not seen a typical 

 specimen. The original description is as follows : shell rimate-per- 

 f orate, sinistral, ovate-conic, obliquely striatulate ; buff with two 

 brown bands on the whorls of the spire, a very narrow one above the 

 suture and a wider one in the middle; the last whorl having a third 

 and wider band below the periphery ; spire whitish, apex small, sub- 

 mammillate. Whorls G, regularly increasing, a little convex, sepa- 

 rated by a linear suture, the last whorl nearly as long as the spire a 

 little inflated. Aperture very oblique, angularly ovate-semilunar, 

 buff in the throat; peristome callous, white, the margins joined by a 

 very thin callus; left margin well arched, reflexed, forming an an^le 

 with the columellar margin, which is vertical, callous, and dilated 

 above, roofing over the perforation. Alt. 32, diam. 20 mill. 



The locality is unknown. The form and coloring described lead 

 me to agree with Fulton that this is identical with Iceris, though the 

 dimensions differ a little from ordinary specimens ; a normal fen's 

 before me 32 mill, long is only 1G mill, in diameter. However, von 

 Martens gives alt. 301, diam. 19 mill, as the measurements of a 

 specimen, and this is as wide as kobelti, 



18. Group of A. adamsi. 



Rather small, sinistral, imperforate or but slightly rimate shells, 

 varying enormously in color and pattern, but no doubt of common 

 ancestry; characteristic of Borneo, but spreading across Balabac 

 Strait to the islands or mainland of southwestern Paragua (Palawan) 

 and on the other side reaching Sumatra and Java. Illustrated on 

 plates GG, 69, 70, 71. 



A wonderful scries of forms, remarkable even in Amphidromus for 

 the instability of coloration. The species are largely arbitrary, for 

 while extreme forms may be remarkably distinct, there are many 

 connecting specimens. In the group of forms included under A. 

 quadrasi the intergradation is demonstrated by series before me ; but 

 the subspecies of the A.adainsi group probably have true racial value. 



A. FURCII.LATUS (Mousson). PI. GG, figs. 38, 39, 40. 



Shell sinistral, long-conic, subperf orate, smooth, glossy; buff-white 

 with grayish-brown flames. \Yhorls 7, a little convex, regularly in- 



