A List of the Crustacea of Wisconsin. 183 



Dr. Hoy found it burrowing in low grounds on the prairies, 

 •emerging from its holes at nightfall and after rains. 



C. ohesics (Hagen). 



This is one of our largest and most abundant crawfish. Unlike 

 most other species, it prefers stagnant water, frequenting ponds 

 and meadow ditches, often wandering far from bodies of surface 

 water, burrowing in wet fields and swales. 



It is pre- eminently our burrowing species, sometimes extending 

 its hole to considerable depths. I once followed a burrow twelve 

 feet without unearthing its occupant or reaching the bottom of 

 the hole. 



This species is easily identified. The rostrum is short, tooth- 

 less, depressed, concave above ; areola wanting ; first abdominal 

 legs of male bifid, with two short, thick, abruptly recurved teeth. 



The annulus of female is transversely elliptical, symmetrical, 

 anterior and posterior margins bituberculate ; fossa 8 shaped, con- 

 stricted in middle by anterior and posterier tubercles ; lateral 

 angles rounded. 



0. hartoyiii. (Erichson.) 



I do not think this species has been found in the interior of the 

 .state. It occurs in Lake Superior. 



It is similar to C. obesus. The rostrum is not so much de- 

 pressed, is less excavated above and the areola is very wide. 



The female annulus has the posterior border elevated and the 

 lateral angles acute. 



Mysas relicta. (Loven.) 



This occurs in the Grreat'Lakes. It has not been found in the 

 interior waters of the state. 



Orchestes dentaius. (Smith.) 



With the exception of Gammarus fasciatus this is the most 

 abundant species in the interior waters of the state. 



Pontoporeia hoyi. (Smith.) 



P. filicornas. (Smith.) 



Both of these species inhabit the deep waters of Lake Michigan. 

 They have never been found in the interior waters of the state, 

 but their occurrence iii the deeper lakes is probable. 



