522 



MOLLUSCA 



narrow; umbilicus closed; height 14 mm.; diameter 23 mm.: America 

 west of the Alleghenies and south of central Michigan. 



P. thyroides (Say) (Fig. 806). Shell depressed, thin, yellowish- 

 brown; aperture with a prominent white tooth on parietal wall; umbili- 

 cus narrow and partially covered by the reflected peri- 

 stome; height 18 mm.; diameter 22 mm.: eastern and 

 central America. 



FAMILY 7. ENDODONTIDAE. 



Shell conical or depressed, ribbed or striated, usually 

 with brown markings, and with open umbilicus; lip thin 

 and sharp, usually without teeth: 4 American genera. 

 Key to the genera of Endodontidae here described: 



a x Jaw composed of a single piece. 



&! Spire raised, but low 1. PYBAMIDULA 



6 a Shell discoid 2. HELICODISCUS 



a z Jaw composed of numerous overlapping pieces; shell 



heliciform (Fig. 772) 3. PUNCTUM 



Fig. 806 



thyroides 

 (Baker). 



1. PYEAMIDULA Fitzinger. Shell with 5 or 6 whorls and a wide 

 umbilicus; aperture rounded and large, usually without teeth; foot with 

 marginal grooves which meet behind; dart sac, mucous genital glands, 

 and flagellum absent; jaw not ribbed, but striated: cosmopolitan; about 

 12 American species. 



Key to the species of Pyramidula here described : 



a t Shell without prominent transverse ribs. 

 Zj Shell color with markings. 



Ci Shell with 2 or 3 revolving bands P. SOLITABIA 



c 2 Shell with broken, irregular transverse bands. P. ALTEBNATA 



& 2 Shell color plain P. PEBSPECTIVA 



a a Shell with prominent transverse ribs P. ASTEBISCUS 



P. solitaria (Say) (Fig. 807). Shell elevated, white 

 or reddish, striped with 2 or 3 broad revolving brown 

 bands; height 19 mm.; diameter 25 mm.: America, north 

 of the Ohio River; Oregon and Washington. 



P. alternata (Say). Shell depressed, yellowish, with oblique and 

 broken red bands ; height 10 mm. ; diameter 21 mm. : eastern and central 

 America; abundant in decaying logs and other damp places; gregarious. 



P. perspectiva (Say). Shell flattened, thin, brownish; aperture 

 small, often with a single small tooth; height 3 mm.; diameter 8 mm.: 

 eastern and central America, but not east of the Alleghenies north of 

 Maryland. 



P. asteriscus (Morse). Shell very flat, with 25 or 30 prominent 

 transverse ribs on the whorls; height .5 mm.; diameter 1.5 mm.: New 

 England and Canada; California. 



Fig. 807 



Pyramidula 



solitaria 



(Baker). 



