154 



HELICID^E. 



" Animal (of P. delibrata) having the left body -lappet of the 

 mouth represented by a simple thickening ; right lappet reaching 

 anteriorly over the back and rapidly becoming narrower below. 

 In P. vittata the sole is distinctly tripartite. 



"Jaw arcuate, the entire anterior surface ribbed, the seven 

 median ribs stronger. In P. vittata there are five very high 

 ribs, strongly denticulating the margin. 



" Radula (of P. delibrata) very long, with 124 transverse rows 

 of 22 (to 18) 20 . 1 . 20 . 18 (to 22) teeth. Central and inner 

 lateral teeth with a large rnesocone and obsolete side cutting- 

 points ; outer laterals and marginal teeth with the ectocone 

 developed. In P. vittata the formula is about the same ; central 

 and inner 14 laterals unicuspid ; outer laterals with an ectocone. 

 At the 25th tooth the mesocone becomes bifid, and outwardly the 

 bifid mesocone becomes shorter, the outermost marginals having 

 three subequal cusps. 



" Genitalia having the female side free from all accessory 

 organs, the duct of the spermatheca very long. Penis terminating 

 in an epiphallus, near the root of which the retractor is in- 

 serted ; epiphallus long, terminating in a short flagellum and 

 the vas deferens. The genitalia of P. vittata are similar ; penis 

 with a spirally coiled flagellum. In P. penangensis the penis bears 

 an epiphallus ending in a short flagellum, and has an accessory 

 sack, perhaps an ' appendix.' 



" These shells are characterized by the deeply descending whorl 

 at the aperture, and the strongly converging ends of the lip. 

 The anatomy is in essential agreement with either Chloritis or 

 Planispira, although the strong ribbing of the jaw is most like 

 the former group. On the other hand, the general form of the 

 shell, the deep descent of the last whorl to the very oblique 

 aperture and the system of colouring, agree more nearly with 

 Planispira. The sculpture of the shell varies considerably in the 

 different species. The more typical, such as fallaciosa, nilagirica, 

 proximo,, as well as vittata exhibit an apparently smooth apex ; 

 but propinqua, tanqueryi, and a few others, show an excessively 

 fine quincuncial punctulation of the apical whorls, such as occurs 

 in Chloritis, in combination with the characteristic shell contour 

 of Trachia. Until we know by the examination of numerous 

 species, how and to what extent the characters of jaw and 

 genitalia are correlated with the above-mentioned shell structures, 

 no consistent zoologist will be justified in drawing rigid lines of 

 demarcation between the Chloritis and Planispiras of South- 

 Eastern Asia. It is better to recognize frankly that in this area 

 the two groups are represented by some forms which, so far as 

 shell characters show, are undifferentiated or separated by feeble 

 characters only." (Pilsbry.) 



Stoliczka was of opinion that faltaciosa, ruginosa, nilagerica, 

 vittata, proxima, and crassicostata pertain to Planispira, s. s., but 

 Pilsbry refers them, correctly I think, to the subgenus Trachia 

 and I have followed him in this respect. 



