1914] Esterly: Schizopoda of the San Diego Region 9 



processes are wanting; there is a well-developed lateral process, but 

 the median lobe, if present, is very short as compared with that of 

 other genera (see pi. 2, figs. 25, 32, and Hansen, 1911, p. 16). 



According to Hansen (1911, p. 17) the only reliable specific char- 

 acters for Nyctiphanes are found in the peduncles of the antennules, 

 and in the sexual appendages of the males. The second and third 

 joints of the peduncles of the antennules are heavier in males than 

 in females (pi. 1, see figs. 8 and 10). The author mentioned, after 

 wide experience in the study of Schizopoda, forms two groups of 

 species in Xyctiphanes, using as a basis the leaflet on the antennule 

 (Hansen, 1911, pp. 19, 20). The numerous specimens obtained here 

 all belong to the second group, in which "the lobe ... is con- 

 spicuously longer than broad, not triangular, with the short acute tip 

 turned mainly or totally outv/ards" (Hansen, 1911, p. 20). The 

 only species in this group is the following. 



Nyctiphanes simplex Hansen 



PI. 1, figs. 6, 8, 10, 13; pi. 2, figs. 20, 25, 28, 32 

 Nyctiphanes simplex Hansen (1911), p. 20. 



It is difficult to ascertain from the brief description of simplex and 

 in the absence of figures whether the San Diego specimens belong to 

 that species or not. As may be seen from figures 8 and 10 (plate 1), 

 the character of the antennular lobe agrees with the account given by 

 Hansen, and, in addition, there is (fig. 8) a spine on the second joint 

 of the antennule which is probably "the oblique spine or an obliquely 

 triangular acute tooth ' ' on the upper surface, at the distal end and on 

 the inner side as described by Hansen (1911, p. 20). In the males 

 the copulatory appendage has no median lobe (Hansen states, p. 20, 

 that it is abbreviated "with no part along the outer margin of the 

 lateral process"), and there are the bristles described by Hansen on 

 the inner margin of the third of the antennule (pi. 1, fig. 10). There 

 is a sexual difference in the form of the leaflet on the basal joint of 

 the antennule (cf. pi. 2, figs. 20 and 28) ; in the female it is rounded 

 at the tip and does not have the strong beak-like process that is present 

 in the male. 



For the present there seems to be no reason why our specimens 

 should not be identified as Nyctiphanes simplex Hansen. 



The length of the egg-bearing females is 14-15 mm., that of adult 

 males is 11-12 mm. Hansen gives the length as 11-16 mm., and the 

 distribution as the tropical and north temperate East Pacific. 



