. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. MESODON. 325 Fig. M. Clarki. ing the umbilicus entirely; one elongated, white denticle on the parietal wall of the aperture. Greater diameter 14, lesser 13 , height, 9 mill. Helix Clarkii, Lea, Proc. Acad. Nat. Sc. Philad., 1858, 41; Journ. — ; Obs., , PI. XXIV. Fig. 111. — W. G. Binney, Terr. Moll., IV. 53, PI. LXXVII. Fig. 10 ; L. & Sh., I. 143 (1869). Xolotrema Clarkii, Tryon, Am. Journ. Conch., III. 48 (1867). Cherokee County, North Carolina; also in Georgia and Eastern Tennessee. It


. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. MESODON. 325 Fig. M. Clarki. ing the umbilicus entirely; one elongated, white denticle on the parietal wall of the aperture. Greater diameter 14, lesser 13 , height, 9 mill. Helix Clarkii, Lea, Proc. Acad. Nat. Sc. Philad., 1858, 41; Journ. — ; Obs., , PI. XXIV. Fig. 111. — W. G. Binney, Terr. Moll., IV. 53, PI. LXXVII. Fig. 10 ; L. & Sh., I. 143 (1869). Xolotrema Clarkii, Tryon, Am. Journ. Conch., III. 48 (1867). Cherokee County, North Carolina; also in Georgia and Eastern Tennessee. It is a species of the Cumber- land Subregion. The lower figure was photographed on to the wood. Jaw as usual, arcuate, ends attenuated, blunt; an- terior surface with about 14 stout, separated ribs, den- ticulating either margin. Lingual membrane long and narrow. Teeth about 35—1—35. Centrals with a stout, short, median cusp, bearing a very short, blunt cutting point, the outer cusps subobsolete. Laterals 15, like the centrals, but asymmetrical. Marginals wide, low, with one inner, short, broad, sharply bifurcated cutting point, and one shorter, outer, bifurcated cutting point; those figured are very bluntly denticulated ; on other portions of the same membrane the cutting points are much more developed and more acute (PI. VIII. Fig. I). The genital system (PI. XI. Fig. G) is peculiar in several respects. The ovary is very slender, and equals about one half the length of the oviduct. The epididymis is highly developed, greatly convoluted, stout, four times the length of the ovary. The oviduct is convoluted. The prostate is greatly de- veloped. The penis sac is short, cylindrical, entering the vagina near its base, and receiving both vas deferens and retractor muscle at its apex. The genital bladder is small, oval, with a short duct entering the vagina about the middle of its length. The vas deferens is swollen on leaving the prostate. Testicle not observed. Mesodon Christ


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