336 GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 



GENUS DARWINULA Brady and Eobertson. 1870. 



''Shell smooth, thin, and fragile. Carapace oblong, higher behind 

 than in front; lucid spots ten to twelve in number, linear-oblong or 

 wedge-shaped, arranged in a subradiate manner in front of the centre 

 of the valve. Seen from the side, compressed, oblong, sub ovate. 

 Seen from above, ovate, acuminate in front, obtusely rounded behind. 

 Valves unequal, the right much larger than the left. Antennules 

 very short, six-jointed, and stout, strongly armed with short and stout 

 curved set?e. Antennre four-jointed, and bearing four or five strong 

 terminal claws; entirely destitute of poison gland or urticaliug sette, 

 the place of which is occupied by a single curved seta of moderate 

 length. Mandible broad, truncated at the distal extremity, which is 

 provided with six or seven small spiniform teeth: palp three jointed, 

 its basal joint very wide and fringed with several curved setae, bearing 

 also a small lamina, fringed with branchial filaments; second joint 

 long, slender, and nearly four times as long as broad, slightly curved 

 and dilated at the distal extremity, where it bears one long and two 

 small setfe; terminal joint more slender, about two thirds of the length 

 of the foregoing, and bearing at the truncate apex about six slender 

 curved spines. First maxilla divided into four short setiferous seg- 

 ments, and bearing a very loog oblong palp, which is fringed with 

 about twenty four long branchial filaments, and has also four other 

 long setfe at its base. Second maxilla simj^le, short, and broad, trun- 

 cate at the apex, and fringed on the distal margin with several slender 

 spine-like hairs, bearing also a large, three jointed, pedilorm palp, and 

 an ovate branchial appendage of moderate size. Two pairs of feet 

 of moderate size, five-jointed; second pair much the longest, and hav- 

 ing the last joint armed with one long and two small curved setie; 

 first three joints of nearly equal length; fourth and fifth, respectively, 

 about one-half and one third as long as the preceding. Abdomen 

 ending in a short conical process. Copulative organs of the male of 

 complex structure, the basal portion of an irregularly shaped plate 

 produced laterally into an aliform process, and on the distal margin 

 into a short, strong hook. Female probably viviparous." (Brady 

 and Norman, 31.) 



Darwinula iniprovisa sp. n. 

 Plate LXXXI, Figs. 1-3, 13. 



Length of female 0.68 mm. Height 0.27 mm. Width 0.24 mm. 

 Length of male 0.70 mm. Height 0.23 mm. 



The right valve is larger than the left and overlaps it on the ven- 

 tral side. In the female the height is more than one-third of the 



