474 



MICHIGAN SURVEY, 1905. 



Subfamily ZONITIN.E Pilsbry. 



^System lacking dart-sack and its accessories. 



Genus OMPHALINA Rafinesque. 



Shell umbilicated or perforated, globosely depressed, thin, striated or 

 wrinkled above, smooth below, reddish horn-color, Ughter below, shining; 

 aperture large, lunar-ovate; peristome simple, straight, acute, extremities 

 approaching, that of the columella subre fleeted. 



Animal (of 0. juliginosd) nearly twice as long 

 as diameter of the shell, blackish or bluish-black; 

 darkest on the head, neck and eye-peduncles, 

 eye-peduncles short in proportion to the length 

 of the animal and set widely apart. Respira- 

 tory foramen in the angle formed by the junc- 

 Fig. 29. Animal of o./Mhffmosa. (Binney).tion of the peristome with the body w^horl. 

 Base of foot whitish, the locomotive band defined by two very fine lines 

 or furrows. A double marginal furrow runs along the side of the foot from 

 the head nearly to the posterior, where it passes upwards and joins that 

 from the opposite side, leaving posteriorly a flattened, rounded extremity, 

 somew^hat prominent and glandular, in the centre of which is a longitudinal 

 sinus, fissure or mucus pore. 



Jaw arcuate, ends acuminated, often recurved, sometimes 



Fig. 30. 



Jaw of o./uhginosa Dg^^i^ioj^. cgutrals with base of attachment longer than wide 



blunt; anterior surface without ribs, cutting margin with a beak- 

 like projection. 



wsa 

 (Binney.) 



with lateral expansions at the corners of the lower margins; laterals of the 

 same type as the centrals, but rendered asymmetrical by the depression of 

 the inner, lower, lateral expansion of the base of attachment and the inner 

 sicle-cusp and cutting point; marginals with narrow, lengthened basal plates, 

 either unicuspid and thorn-like or bicuspid by elevation of outer on middle 

 cusp. 



Fijr. .31. 



.ion of O. f}(ligi)uis:i. (Binney.) 



KEY TO THE SPECIES OF OMPHALINA. 



I. Shell larger, 26 mm. in diam.. umbiUcus wide fuliginosa. 



II. Shell smaller, 15 mm. in diam, umbiUcus minute inornata. 



OMPHALINA FULIGINOSA (Griffith). 



Shell rather large, thin, depressed, chestnut brown 

 sometimes almost black, shining and wrinkled; whorls 4^, 

 rapidly increasing, the last whorl very voluminous and 

 expanding transversely toward the aperture ; suture 

 slightly impressed; aperture very oblique, ample, lunate- 

 ovate; peristome simple, thin, with a light testaceous de- 

 posit within, extremities approaching that of the colu- 

 mella somewhat reflected; umbilicus deep and much ex- 



Fig. 32. 0. fuliginosa. Ponded. 

 (Binney.) 



