. Bulletin - United States National Museum. Science. 74 A MANUAL OF AMERICAN LAND SHELLS. I have not examined the jaw or lingual membrane of this species, but am entirely dependent on Morse for the descriptions and figures of the American form given above. Fig. Animal of 77. lineatus, enlarged. (Voise.) Fig. 35. HELICODISCUS, Morse. Animal heliciform; mantle posterior, thin, simple, protected by a shell; other characters as in Patula. Shell discoidal, widely umbilicated, not shining; si)ire concave; whorls 4, equally visible above and below, the last scarcely larger than the rest, not def
. Bulletin - United States National Museum. Science. 74 A MANUAL OF AMERICAN LAND SHELLS. I have not examined the jaw or lingual membrane of this species, but am entirely dependent on Morse for the descriptions and figures of the American form given above. Fig. Animal of 77. lineatus, enlarged. (Voise.) Fig. 35. HELICODISCUS, Morse. Animal heliciform; mantle posterior, thin, simple, protected by a shell; other characters as in Patula. Shell discoidal, widely umbilicated, not shining; si)ire concave; whorls 4, equally visible above and below, the last scarcely larger than the rest, not deflected; aperture rounded, vertical; several pairs of tubercles at intervals within, on the inner surface of the outer whorl; peristome simple, straight, its margins distant. Jaw, according to Morse, of S. lineatus, low, wide, crescentic, ends much attenuated, acute; cutting margin with a median, beak-like projection; anterior sur- jaw of H. lineatus. facc without ribs, but covcrcd with striai con- verging obliquely towards the beak-like prominence. Fig. 36 shows the general arrangement of the teeth upon the lingual Fig. 36. membrane. The characters I of the separate teeth are better shown in Plate IV lof T. M., V, Fig. M. Morse ^ gives 77 rows of 12-1-12 Lingual dentition of if. ii/ieatws. (ilorse.) teeth Cach witll 4 PCrfcct laterals. Leidy, in T. M., Vol. IT, 262, Fig. gives 13-1-13 teeth, with 5 i)erfect laterals. The membrane examined by me has 12-1-12 teeth, with 4 perfect laterals. The central teeth have a base of attachment very small, longer than wide, with expanded lower angles and reflected upper margin. Ketiection very small, with a stout, short median cusp, and very short, blunt side cusps, all the cusps with short cutting points. The lateral teeth have a base of attachment three times as wide, and somewhat longer than the centrals, and asymmetrical by the suppres- sion of the inner, lower lateral expansion; the upper margin is broadly reflected; the reflection is s
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