226 GEOL. AND NAT. HIST. RUEVEY OF MINNESOTA. 



in front and the anus at the end of the post-abdomen. Many eggs are 

 produced at once. The male opening is at the base of the abdomen, 

 as in Sididce. The general habitus is, however, lynceid. The males 

 appear in autumn or when, by the gradual drying up of the water 

 or other causes, the continued existence of the animals is threatened. 



GENUS EURYCERCUS Baird. 

 Characters of the sub-family. 



Eurycerciis lamellatiis O. F. MuUer. 



Plates XLVI, Figs. 7, 8; LI, Fig. 6; LX, Figs. 5, 6; LXII, Fig. 19. 



Lynceuslamellatus — MnelleT, Edwards, Koch, Zaddach, Lievin, Ley dig, Zenker. 

 Eurycercus laticaudaiiis — Fischer, Schoedler. 



A gigantic Li/nceid, reaching the dimension of 3.0 mm. The figure 

 of the male given will sufficiently illustrate the general form. The 

 abdomen is broad and armed behind with a dense row of saw teeth. 

 The eye is larger than the rather small pigment fleck, and the intes- 

 tine is bent upon itself but not coiled. The last foot is found in few 

 other Lynceidce. Acroperus has the same, and Pleuroxus unidens also 

 has a rudimentary sixth foot. 



SUB-FAMILY LYNCEINJ]. 



Intestine coiled; anus near the end of the post-abdomen; opening 

 of vas deferens nearly terminal. There are no anterior cteca but 

 usually a single anal diverticle of the intestine. Rarely or never more 

 than two embryos produced at once. 



KEY TO THE SUB-FAMILY LYNCEIN^. 



I. Head or dorsal line keeled or ridged; abdomen long; shell marked with 

 diagonal strije. 

 > Camptocei'cus, 227, 228; Acroperus, 227; Alonopsis, 231 



II. Usually no keel above, or, if keeled, the post abdomen is not long. The 

 majority are highly arched dorsally, and have comparatively short post- 

 abdomen and pointed beak. The antennae are usually feeble and the 

 motion slow. 



A. Post-abdomen nearly round in outline, armed with very long, stout 



spines, terminal claw with one minute basal spine or none; greatest 

 height of shell about equal to the posterior margin. . Ijeydigia, 233 



B, Post-abdomen more or less triangular, armed with bristles; greatest 



height of shell moderately exceeding that of the posterior margin; 

 shell marked with hexagonal meshes. 



