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



eggs, and is less slender than the adult. The fact that all these species 

 are heterogenentic has been frequently reported by the writer. 

 Length 1,2 to 1.3 mm. Antenna 1.3 to 1.5 mm. Marsh found the 

 species but once, near Marquette. 



* Diaptomiis piscintie Forbes. 

 Plate V, Fig. 13. 

 Forbes '93. 

 A species of medium size (1.75 mm. long), having the last thoracic 

 segment not produced but armed with spines. The fifth feet of the 

 female has the apical segment of the outer ramus obsolescent and the 

 long one jointed inner ramus provided with sjiines half as long as the 

 ramus. The male feet are very like those of D. leptopus. The outer 

 ramus of the left foot has a quadrate basal joint much wider than the 

 second segment, which bears a small blunt spine and a long curved 

 seta. The inner ramus is nearly as long as both the segments of the 

 outer, and terminates in a broadly rounded, or subtruncate, thickly 

 ciliate end. The terminal claw of the outer ramus of the right leg is 

 short, ciliated; the accessory spine being near its base. The inner 

 ramus is longer than the basal joint of the outer, terminating in a 

 blunt ciliated end. 



Diaptomiis laciniatus Lilljeborg. 

 Plates VIII, Fig. 15; X, Fig. 12. 

 De Guerne and Richard '89. 

 This alpine and northern form may be at once recognized among 

 its congeners by the fact that the two last thoracic segments are pro- 

 duced on either side into large projections, of which those of the last 

 one are enormous and are armed with two minute spines. The first 

 abdominal segment is as long as the rest of the abdomen. Caudal 

 stylets short. The antennae extend beyond the stylets. Length with- 

 out stylets 1.8 mm. to 1.2 mm. 



Diaptomiis castor (Jurine.) 



Plate IX, Fig. 5. 



Jurine '20 (Monoculus castor): Koch '35 (Glaucea rubens); Lilljeborg '53; Lubbock 



^Q^\ De Guerne and Richard '89. 



The confusion of several species under this name and loose de- 

 scriptions of European authors stood in the way of any differentiation 

 of non-European species until very recently. In fact, until the ap- 

 pearance of De Guerne and Richard's work no writer could feel safe 

 in the attempt to distinguish species in this genus. All references to 

 D. castor in America are erroneous. In our own case D. Uptowns has 

 been most often so called. 



