GASTROPODA— -PAL2EACM2E1D2E. 



603 



66. Carina sharp, when perfect drawn out into high collar ; 



apertural notch deep LIV. Eccyliopterus. 



IX. Shell coiled 22. 



22. Cylindrical or oval, generally narrowing towards aperture 30*. 



30*. Aperture incomplete, oblique or anterior <\ f . 



q / . Columella and outer lip with teeth 67. 



67. Columella with callus, aperture with rounded posterior 



notch CCX VI . Anthracopupa. 



67. Columella without callus, no posterior notch. 



CCXV. Pupa. 



q / . Columella and lip without teeth ; center of outer lip nearly in 



axial line of shell CCXVII. Dendropupa. 



Family Pal^eacm^id^: * Grabau and Shimer. 

 I. Triblidium Lindstrom. (Emend. Berkey.) 

 Patelliform obovate shells, narrowest anteriorly, often acuminate ; 

 conical with beak varying from nearly marginal to overarching 

 anteriorly ; muscular scars in rings of seven or eight disconnected 

 pairs ; anterior pair meeting in front beneath the beak. Lines of 

 growth, and rarely obscure broad radial plications, mark the sur- 

 face. Cambric-Ordovicic. 

 1. T. rectilaterale Berkey. (Fig. 802, a, b.) Cambric. 



FlG. 802. a, b, Triblidium rectilaterale ; c, d, T. convexum ; <?, f, T. barabuensis. 

 (After Berkey, Am. Geol., 21.) 



Large, conical, high, with straight sides and apex somewhat 

 behind the front ; aperture ovate-acuminate. 

 St. Croix (Dresbach) of Minnesota. 



* The names starred are new. 



