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FRESH-WATER BIOLOGY 



SO (si) Carapace short, three-fifths as long as exposed abdomen; telson with 

 one (or two) median and two lateral spines on its dorsal 

 median third. . . Apus lucasanus FstckaTd iSji 



An abundant and widely distributed species; reported from Lower Cali- 

 fornia and Kansas. 



Fig. 1035. Apus lucasanus, Telson. X 6. (After Packard.) 



51 (so) Carapace even shorter than in A. lucasanus; telson very short with 



one median and four lateral spines on dorsal median third. 

 Apus lotigicaudatus Leconte 1846. 



This form occurs in Colorado, Nebraska, Texas, and along the Yellowstone 

 River. 



Fig. 1036. Apus longicaudaius. Telson. X 6. (After Packard.) 



52 (37) Body compressed, carapace forming two lateral valves which enclose 



the body Suborder Conchostraca . . $^ 



53 (60) Only the first post-cephahc limbs prehensile in the male; carapace 



spheroidal, without lines of growth; head not included 



within carapace-chamber Family Limnetidae. 



Only one genus Limnetis . 54 



54 (57) Shell subspherical. . ... 55 



55 (56) Length, 3 mm.; front of male's head narrow; second antenna i6-seg- 



^ ^ mented; flabellum very large. Limnetis gouldii 'BeaiA. i?:62. 



A form widely distributed through Massachusetts, New 

 Hampshire, Rhode Island, New York, Illinois, and Canada. 

 It is very hardy and will live for months in aquaria. 



Fig. 1037. Limnelis gouldii. ^ , head of male, dorsal view. X 21; 

 B, shape of shell. X 7. (After Packard.) 



56 (ss) Length, 4.2 mm.; front of male's head very broad; antenna 20-seg- 



mented Limnetis gracilicornis Packard 1871. 



This species was described by Packard from specimens collected 

 at Waco, Texas. 



<^ 



Fig. 1038. Limnetis gracilicornis. Head of male, dorsal view. 

 (After Packard.) 



X18. 



57 (S4) 



58 (59) 



Shell suboval 38 



Length, 4 mm.; front of male's head broad and square; second an- 

 B tenna 14- and 17-segmented; flabellum very narrow. 



Limnetis mucronaius Packard 1875. 



This species has been reported from Montana and Kansas. 

 It is easily recognized by the mucronate, tridentate front. 



Fig, 1039. Limnetis mucronaius. X , head of male, dorsal view. X 20; 

 B, shape of shell. X 4. (After Packard.) 



Length, 4 (to 6) mm.; front of male's head rather broad; second 

 B antenna 29-segmented; flabellum short and broad. 



Limnetis brevifrotts Packard 1877. 



This is the largest known species of this genus in North 

 America. It has been observed only at Ellis, Kansas. 



Fig. 1040. Limnetis hrevifrons. A, head of male, 

 of shell. X 3. (After Packard.) 



X 8. B, shape 



