STATE GEOLOGIST. 253 



DECAPODA. 



But two species of Cambaru.% C. virilis. Hagen, and C. signifer, 

 occur in Hennepin county, except, perhaps, in the Mississippi. The 

 following localities for the former species are known in the State: 

 Mississippi river, Minnehaha creek, Bassett's creek, Cedar lake. Lake 

 Minnetonka, Lake Independence, Lake Superior. 



It is possible to recognize three age-forms in the males of this species. 



A. The immature male (II Form, Hagen). Reaching two to three 

 inches in length, this stage has the chelae proportionally smaller, and 

 the spinous armature less developed: the first abdominal foot is simply 



bifid at the end. i ip . i. 



B (Form I of Hagen,) usually over two and one-half inches long; 

 chelse larger; branches of abdominal foot destinct; inner branch 

 grooved but lance -linear. 



C Very large (four inches) ; inner branch of abdominal foot spatu" 

 late'at end; the two rows of tubercles on the inner margin of the 

 " hand " with six or seven in a row instead of five. 



Male of Form II, A stage, 2i in. long. Chela. 7 in., thumb .49 in. 



" I, B stage, 2i in. long, " 1 in., '' .6 in. 



u a I^ C stage, 4 in. long, " i.8 in., " 1.1 in. 



" II, A stage, 3 in. long, " 1.2 in., " .75 in. 



It will be seen from the above that size does not govern the transi- 

 tion from the first to the second form entirely. This differs either in 

 different localities or at different seasons of the year. A large gather- 

 ing from Cedar lake showed no specimens of the form I, while a 

 similar gathering at Lake Independence contained but one of the form 

 II A male from Minnehaha creek had rudiments of a third tooth on 

 the carpus of the left claw, thus indicating an approach to Hagen's 

 Var A. . 



CAMBAKUS SIGXIFER sp. nOV. 



(Fig. T.) 



A slender, o-raceful species of raiher marked colors, belonging to the 

 section having a hook on the third pair of legs but not on the fourth. 

 The rostrum is not carinated nor toothed at the apex; acumen moder- 

 ate lateral borders curved, moderately excavated. Cephalothorax 

 arched and not depressed above, densely punctate; areola hnear; 

 chelae slender, straight; thumb deeply excavated on the inner margm 

 for the proximal one-third: opposite finger with an impressed groove on 

 the inner but not on the outer margin. 



