282 A MANUAL OF AMERICAN LA]\D SHELLS 



The coloring exhibits every shade from light amber to dark chestuut, 

 sometimes with a revolving band, and then known as var. cincta* The 

 whorls of some revolve about the axis at such a distance as to leave a 

 deep and wide umbilicus {monodon), while in others they are in such 

 near approximation as to permit only a small perforation, which the 

 narrow, reflected peristome is sufficiently wide to cover (fraternum). 

 The hairy projections of the epidermis are most distinct upon the young 

 shells, but are often wanting at every stage of growth. The oblique 

 striae are so fine as hardly to be visible, and in some instances the shell 

 appears to be glabrous. Very beautiful si)ecimens, about one-fourth of 

 of an inch in diameter, with a dark, shining epidermis and open umbili- 

 cus, occur in Oliio, Indiana, Iowa, and Michigan. They are more convex, 

 and as the same number of volutions is contained in half the space, they 

 appear to have more whorls thau the common variety. Some i)ersons 

 have considered these to form a distinct species [H. Leaii, Ward, MS.); 

 but I do not see that they can, with i)ropriety, be separated. 



In the Western States this species is generally found in the forests. 

 In New Hampshire and Vermont it is also found in forests with other 

 species, but more commonly in hill-side pastures, under flat stones, a 

 situation where other species rarely occur. Two individuals are com- 

 mon I3' found together. 



Fig. 300 is drawn from a curious pathological specimen. 'The peri- 

 stome having been broken after the animal's arrival at maturity, a new 

 Fig. 300. peristome has been formed somewhat in the rear of the first, 



^'^^,.^>) and a new parietal tooth added. The base of the shell was 

 purposely broken to show the position of the internal tubercle. 

 ii.monodon. r^]^Q jaw of iS. mouodon is slightly arcuate, stout, bluntly 

 rounded at ends ; anterior surface with broad, stout ribs, denticulatiug 

 each margin (Fig. 288). 



8. monodon (Terr. Moll., Y, Plate VII, Fig. H) has 21-1-21 teeth on 

 its lingual membrane ; 10 perfect laterals ; the thirteenth tooth has a 

 bifid inner cutting point. Morse gives 28-1-28 teeth. 



The characteristic feature of the genitalia is the penis sac. It is 

 unproportionally long, club-shaped, and greatly enlarged above, where 

 it receives both vas deferens and retractor muscle. The genital blad- 

 der is small, elongate-oval, on a short, delicate duct. The epididymis 

 is convoluted in its whole length (Plate XI, Fig. L, of Terr. Moll., V). 



* Hayesville, N. C. See Lewis, Proc. Phila. A. N. S., 1874, 1G2. 



