STATE GEOLOGIST. 43 



Sp. 2. Seaplioleberis corniita, SchceJler. 

 (Plate T. Fig. 6.) 



Monoculus bispiiiosus, DeCtKKR. 



Daphnin mucronata, var. acute rostrala. Baird. 



Scapholeberis mucronata, var. f route cornula, P. E. MUELLER. 



This species diflfers from the above only in having a sharp curved 

 horn on the head in front of the eye. The use of this appendage- 

 can only be coujectured; but it may be that, like the curved beak 

 of Ripophilus, it serves to clear away rubbish in the filth in which 

 these animals frequently live. This form, be it variety or species^ 

 is not known in America. 



Sp. 3. Scapholeberis ariuata, (Henick.) 

 (Plate B. Figs. 10-11.) 



Scapholeberis mucronata. var. armata, Heeeick. 



A very beautiful and unique species, which possesses the extreme 

 development of the peculiarities ot the genus. The head is shaped 

 very much as in the previous species, the fornix is squarish, th& 

 basin for the antennae is small. The upper lines from the fornix 

 meet behind the eye; the form of the shell is as in the above, but 

 the spines upon the lower margin are longer. The scythe-like 

 spine on the lower angles of the valves is extremely long, falling 

 little short, in extreme cases, of being as long as the entire lower 

 margin, in others about one-half as long. There are the usual 

 lines parallel to the lower edge of the shell. The specimens hav- 

 ing the longest spines were found in fresh water about Mobile, 

 Ala., but the species occurs in Minnesota and intermediate points^ 

 though sparingly. 



Sp.4: Scapholeberis nasuta, Birge. 



Form much as in the last, head shorter, "prolonged into a 

 rather sharp beak, at whose apex the continuations of the fornices 

 unite. The beak does not project downward as in S. mucronata, 

 but backward, and in its natural position lies between the valves." 

 The usual reticulated and lined areas are present and the balance of 

 the shell is covered with ''small pointed projections." "The anten- 

 nules are much larger than in S. mucronata, though they do not 

 project beyond the rostrum." The pigment fleck is long and 

 large; the post-abdomen is much as in the preceding species; the 

 terminal claws have several fine teeth. The males have the open- 



