GASTROPODA— LOXONEMATIDM. 



691 



folds indistinct ; lines of growth often undulating and imbricating 

 in adult portion. Commonly adhering to crinoids. 



Burlington of Iowa and Missouri ; Keokuk of Iowa, Illinois, 

 and Indiana. 

 .271. I. subplicatum Meek and Worthen. (Fig. 984.) 



Mississippi. 



Small, depressed conical, rapidly expanding, beak excentric ; 

 folds coarse, irregular, few. 



Waverly of Ohio ; Chester of Illinois. 



Family Loxonematid/E Koken. 

 LXXVIII. Acanthonema Grabau. 

 Turreted shells, with gradually enlarging round whorls marked 

 foy three (rarely two) spirals, one or more of which are nodose. 

 Type A. holopiforme Grabau. Siluric. 



272. A. holopiforme Grabau. Siluric. 

 Short, rather thick, round whorled, lower 



spiral covered except on body whorl ; upper 

 two nodose. (Middle one absent in var. 

 •obsoleta.) 



Upper Monroe of Michigan, Ohio, and 

 Canada. 



273. A. laxum Grabau. Siluric. 

 Long and slender, whorls six or more, 



-all three spirals visible, upper two nodoso- 

 spinose. 



Upper Monroe of Michigan, Ohio, etc. 



274. A. newberryi (Meek). (Fig. 985.) 



Siluric. 



More slender than preceding ; nodulations chiefly confined to 

 upper spiral.* 



Upper Monroe of Ohio and Michigan. 



LXXIX. Callonema Hall. 

 Broad and rather low-spired,, umbilicated shells with round or 

 subangular whorls, thin outer lip, and thickened columellar lip 

 spread over volution above and extended below. Surface with 

 iregular, sharp, transverse striae. Devonic. 



Fig. 985. Acanthonema 

 newberryi, nat. size and 

 enlarged. (After Meek, 

 Pal. Ohio, I.) 



