1914] Esterly: Schizopoda of the San Diego Region 5 



Key to the Genera op the Euphausiacea 



1. None of the first six thoracic limbs with the inner ramus noticeably elong- 

 ated; cornea of eyes not biblobate (pi. 1, figs. 6, 8, 9, 13) 2 



1. Second or third thoracic limb with noticeably elongated inner ramus; cornea 



of eyes more or less bilobate (pi. 1, figs. 1, 3, 4) 4 



2. The inner ramus of the seventh thoracic limb consists of two long joints; 



there is an upstanding leaflet that points backward on the basal joint of 

 the peduncle of the first antenna (pi. 1, figs. 6, 8, 13) NyctipJianes 



2. The inner ramus of both the seventh and eighth thoracic limb is rudimen- 



tary; no leaflet on the basal joint of the peduncle of the first antenna —.3 



3. The outer ramus of the seventh thoracic limb is developed as in the first six; 



the inner ramus is lacking from the seventh limb in males 



Thysanoessa (part) 



3. Both rami of the seventh and eighth limbs very rudimentary in both sexes, 



being reduced to inconspicuous bristles EupJiausia 



4. The inner ramus of the second thoracic limb is elongate 5 



4. The inner ramus of the third thoracic limb is elongate Stylocheiron 



5. The inner ramus of the second thoracic limb is very long and slender; there 



are no bristles along the margins of the penultimate joint (pi. 2, fig. 35) 



._ ....Nematoscelis 



5. The inner ramus of the second thoracic limb is elongated, but rather stout; 

 there are bristles along both margins of the penultimate joint (pi. 2, fig 

 31) - Thysanoessa (part) 



FAMILY EUPHAUSIIDAE 



Subfamily Euphausinae Holt and TattersalI; 



' ' Eyes not or only slightly bilobate. None of the legs much longer 

 than their immediate fellows, nor terminating in brushes or claws. 

 Palps of maxillae simple" (Holt and Tattersall, 1905, p. 101). 



Genus Euphausia Dana 



EupJiausia, Sars (1885), p. 63. 

 Euphausia, Zimmer (1909), p. 12. 

 Euphausia, Hansen (1910), p. 89. 

 Euphausia, Hansen (1911), p. 21. 



Euphausia is most readily separated from the other members of 

 the family by the condition of the last two pairs of legs (Sars, 1885, 

 p. 64; Zimmer, 1909, p. 12). Both are very much reduced, being 

 merely bristle-like processes hidden among the bushy gills. Hansen 

 (1911, p. 21) has given an account of the various species of Euphausia, 

 which may be grouped according to the number of lateral denticles on 



