THE NAUTILUS. 89 



and Pupillida are the most prolific of the land forms. The 

 PupiMda represented by five ?pecies, are by far the most abun- 

 dant of the land forms, Bifidaria procera and cristata occurring 

 in colonies of hundreds. Bifidaria contracta Say, however is 

 quite rare, being known only from a few specimens taken from 

 the stomach of a lizard. 



Among the specimens of the Zonitidce, Vilrea indentata Say 

 and Zonitoides aborea Say are very plentiful in suitable spots, 

 while Eucomdus fulvus Drap. is rare, although the latter is 

 adapted to like environment in other regions. Succinea avara 

 Say is very abundant along the margins of small streams and 

 ponds where the soil is damp and well shaded. 



Following each species we have given measurements of the 

 average sized, mature shells from the various stations in which 

 we collected in the county. These measurements may be ac- 

 cepted as representing the size acquired by each species in this 

 particular region of Oklahoma. 



Hdicida. 



Polygyra monodon Rack. Alt. 5.2 mm., diam. 8.5mm. 

 Polygyra texasiana Moric. Alt. 4.3 mm., diam. 9.3 mm. j 

 Polygyra texasiana var. Alt. 5.2 mm., diam. 11.7 mm. 



Pupillidx. 



Bifidaria armifera Say. Alt. 4.6 mm., diam. 2.8 mm. 

 Bifidaria contracta Say. Alt. 2.6 mm., diam. 1.4 mm. 

 Bifidaria procera, Gld. 



Bifidaria p. cristata P. & V. Alt. 2.8 mm., diam. 1.2 mm. 

 Pupoides marginatus Say. Alt. 4.8 mm., diam. 2.0 mm. 

 Strobilops labyrinthica Say. Alt. 2.2 mm., diam. 2.4 mm. 

 Vertigo ovata Say. 



Zonitidtz. 



Eucomdus fidvus Drap. Alt. 2.9 mm., diam. 2.8 mm. 

 Vitrea indentata, Say. Alt. 2.1 mm., diam. 6.0 mm. 

 Zonitoides arborea Say. Alt. 1.9 mm., diam. 4.5 mm. 

 Zonitoides minnscula Binn. Ait. 0.9 mm., diam. 2.1 mm. 



Limacidse. 



Agriolimax agrestis Linn. 



