4 PROCEEDIISrGS OF THE NATIONAL MUSEUM voc^ 82 



KEY TO THE SPECIES OF LIMNOCALANXJS 



1, Botli exopods of male fifth feet 2-s:egmented, length of lurcal 



rami about seven times width 2 



Right exopod of male lifth feet distinctly 3-segmented, length 

 of furcal rami about three times width johanseni Mursh 



2. Head distinctly vaulted, with a cervical depression; sides of 



last thoracic segment rounded ; female antennae hardly reach- 

 ing second abdominal segment. Fresh water macrurus Sara 



Head not distinctly vaulted, no cervical depression ; sides of last 

 thoracic segment pointed ; female antennae extending to base 

 of furca. Marine and brackish water grimaldii (de Gueniej 



LIMNOCALANUS MACRURUS Sars 



Plate 1, Figxjkes 2, 3, 5 ; Plate 2 ; Plate 3, Figures 1-3 ; Plate 13, Figuiie 5 



Limnocalanus macrurus Sars, 1863, pp. 228, 229; 1903, pp. 81-83, pis. 55, 56. — 

 Forbes, 1882, p. 648.— Nordquist, 1888, pp. 31-37, pi. 1, figs. 9-11, pi. 2, 

 figs. 1-5, pi. 3, figs. 1^.— DE GuERNE and Richard, 1889, p. 77, pi. 4, figs. 

 5, 11, 12.— Herrick and Tuener, 1895, p. 49, pi. 1, figs. 1^.— Schacht, 

 1898, pp. 238-244.— Giesbrecht and Schmeil, 1898, pp. 58, 59. — Maksh, 

 1918, p. 774, fig. 1212. 



Limnocalanus macrurus var. auctus Forbes, 1891, pp. 706, 707. — Marsh. 1893, 

 p. 201, pi. 4, fig, 7 ; 1895, pp. 11, 12, pi. 4, figs. 1, 2, pi. 5, figs. 1-3. 



Lunnocalanus grimaldii var. macriirus Rylov, 1922, pp. 13, 14, fig. 5, (x-d; 1930, 

 pp. 64-69, fig. 5, 1 and 2, fig. 13, 3 and 4, fig. 15, 1^. 



The head, seen in profile, is distinctly vaulted, and there is a more 

 or less clearly marked cervical depression. (PL 1, figs. 2, 3.) The 

 last cephalothoracic segment is not broadened, and its sides are 

 rounded. There are spines on the distal border of the second ab- 

 dominal segment of the female and on segments 2 to 4 of the male. 

 The length of the furcal rami is about seven times the width. The 

 first antennae hardly reach the second abdominal segment. The 

 armature of the first antennae of the male is shown in Plate 2. The 

 exopod of the second antenna has the typical form of the genus. 

 (PI. 1, fig. 5.) 



In Plate 3, Figures 1 and 2, are shown the swimming feet 1 and 

 2, and in Figure 3 the fifth foot of the female. 



In the male fifth foot (pi. 13, fig, 5), the right exopod is 2-seg- 

 mented, but the second segment has a projection that may be con- 

 sidered as a rudimentary third segment; the right exopod and 

 endopod are of about equal length. The left exopod is larger than 

 the endopod. 



The size, as given by different authors, varies somewhat : Females, 

 2.2 to 3.15 mm ; males, 2.2 to 2.78 mm. 



This species is considered a fresh-water form. It occurs in many 

 localities in Scandinavia and in Finland, In America it is in all 

 the Great Lakes, in Green Lake, Wis., and in Lake Nipigon, Canada. 



