70 HELICID^E. 



shell ; tentacles very short, eye pedicles of moderate length. 

 Mantle-edge thin, with small right and left body-lappets. Pul- 

 monary cavity small. Kidney large, triangular. 



"Jaw very thin, horny, arched, with a small anterior median 

 projection ; it is marked transversely with a great number of 

 more or less distant grooves which divaricate in the centre. 

 Eadula of moderate width, long, composed of about 100 trans- 

 verse more or less V-shaped rows of 60-70 teeth. Central tooth 

 smaller, sometimes much smaller, than the laterals, very narrow, the 

 reflection small, with three slender cusps. Lateral teeth with 

 a large inner cusp and simple or bifid outer cusp, and a minute 

 inner cusp. 



" Genital system having the duct of the spermatheca long. An 

 organ of unknown homology (either a dart sack, a diverticulum 

 of the spermatheca, or an appendicula) enters the vagina just 

 above the opening of the spermatheca duct. Uterus containing 

 few large eggs. Penis simple, receiving the vas deferens and the 

 penis retractor at its apex, the latter attached distally to the floor 

 of the lung cavity." (Pilsbry.) 



Stoliczka was the first to investigate the anatomy of Plectopylis 

 (1871), four species, acJiatina [bensoni], cyclaspis, pinacis, and 

 macromphalus, forming the subject of his memoir. It was not until 

 thirty-six years subsequently (1907) that Lt.-Col. Godwin-Austen 

 followed with an account of the anatomy of P. cyclaspis. Stoliczka 

 states that on the whole the form of the body closely resembles 

 that of Clausilia, and that a comparison of the interior organiz- 

 ation of the two genera also indicate their close relation. The 

 jaw he found similar in structure but different in shape. Much 

 greater, he continues, is the similarity of the Plectopylis jaw to 

 that of Cylindrella, with the exception that the median projection 

 is wanting in the latter. The arrangement of the teeth of 

 P. acJiatina [bensoni'] and P. cyclaspis he also found to agree with 

 that of Cylindrella in the very small size of the centre tooth, but 

 this was not found to be a constant character. In P. pinacis the 

 centre tooth was larger and more of a shape similar to that of the 

 lateral teeth, which, however, in all the species he found to retain 

 distinctly the helicoid character. 



Godwin-Austen found in P. cyclaspis the penis simple, like that 

 of Gorilla, but very short in comparison with the great length of 

 the rest of the genitalia and other organs occupying the closely- 

 wound many-whorled shell. He states that the vagina soon de- 

 velops into the thin-walled oviduct, which was found occupied 

 by about a dozen embryonic shells in various stages of develop- 

 ment, the anterior ones, very well grown, showed the coiled visceral 

 sac, and were covered with minute calcareous granules. The 

 spermatheca was a thin cord with a sac-like expansion at the 

 free end. The hermaphrodite duct was long, convolute, and 

 lying attached to the side of the albumen-gland. 



The intestine was long and cord-like, the salivary glands small 



