OF CONCriOLOGY. 259 



STROBILA, Morse. 

 1. Strobila labyrinthica, Say, 



Plate 4, figure 44. 



Obtuse-conic, brownish; whorls 6, heavily ribbed above, 

 more slightly so beneath, suture well impressed, lip thickeaed, 

 somewhat reflected, with two revolving larniniie upon the base, 

 not visible from the aperture, but seen through the shell. Upon 

 the body are three revolving laminas, and on the columella 

 another. Base flattened, umbilicus small, impressed. 



Diarn. 2i height 2i mill. 



Maine to Maryland, Mississippi, Texas, Arkansas, Western 

 States. 



2. Strobila Hubbardi, Brown. 



Plate 4, figure 45. 



Depressed, thin, striated above, smooth beneath, brownish, 

 thin; whorls 5, with two parietal revolving laminae, and two 

 more far within on the outer whorl ; umbilicus rather wide, 

 lip slightly reflected, 



Diam. 2i, height li mill. 



Indianola, Texas. 



May be distinguished from No. 1 by the teeth being more 

 depressed and having a large umbilicus. 



PATULIN^. 



Genera, 



1. Anguispira, Morse. Shell heavy, large, depressed- tur- 



binate, solid, ribbed-striate, banded or stripedj umbilicus 

 moderate ; aperture not toothed. 



2. Patdla, Hald. Shell moderate, rather heavy, discoidal. 



a little convex above, concave below, ribbed-striate, 

 unicolored ; umbilicus very ivide but shallow, exhibiting 

 all the volutions. 



3. Plaxogyra, Morse. Shell minute, perfectly flat above, 



umbilicus moderate ; whorls very convex, the last one 

 crossed by from 20 to 25 sharp raised ribs. Unicolored, 



4. IIelicodiscus, Morse. Shell minute, planorboid; whorls 



equally visible above and bolow, revolving on the same 

 plane, externally with revolving stride ; aperture lamel- 

 larly toothed within the outer lip. Unicolored. 



