FOSSILS OF THE CAKBONIFEKOUS. 



261 



FIG. 4. Outline 

 figure of a typi- 

 cal shell, X 3. 



Genus AMPULLARIA Lamarck. 



Ampullaria ? Powelli Walcott. 

 [mpullaria f Powelli Walcott, 1883. Science, vol. ii, p. 808, figs. 3, 3 a. 



Shell subglobose; umbilicus small; spire depressed; volutions three or 

 four, increasing uniformly in size until the last one, which is larger in pro- 

 portion and slightly expanded at the aperture; suture dis- 

 tinct; aperture oblong, broad ovate, and a little straightened 

 on the inner side, entire; peristome continuous, slightly 

 reflexed. 



Surface marked by fine lines of growth. Operculum 

 concentric, rather thick, and of a calcareous or shelly struct- 

 ure; nucleus subcentral. 



In referring this species to the genus Ampullaria we 

 bear in mind that it is not probable that a genus of this 

 character has continued from the Middle Paleozoic to the 

 present time; on the other hand, when we consider that the 

 shell is Ampullaria-like in character and associated with an operculum that 

 is almost characteristic of the genus, that the genus Pupa is known from 

 the Middle Carboniferous, and that a shell not to be distinguished from 

 the recent Physa is associated with Ampullaria f Powelli, a pulmonif- 

 erous shell Zaptychius Carbonaria and a twig of a coniferous tree, all of 

 which are evidences of a near land area, it would appear that a reference 

 to Ampullaria, as the genus representing the group to which the species 

 belongs is warranted by the facts, although it may be ultimately referred to 

 a new genus or subgenus. 



Formation and localities. Lower portion of the Carboniferous Group, 

 on the western slopes of New York and Richmond Mountains, Eureka Dis- 

 trict, Nevada. 



FIG. 5. Opercu- 

 lum, X 3. 



PULMONIFERA. 



For an excellent summary of what was known of the Paleozoic rep- 

 resentatives of this subclass up to the month of November, 1880, we are 

 indebted to Dr. J. W. Dawson, who states that the three known localities of 

 their occurrence are on the American continent, and that six species were 



