1914] Esterly: Schizopoda of the San Diego Region 11 



Thysanoessa gregaria Sars 



PI. 1, figs. 5, 16; pi. 2, figs. 24, 31 



Thysanoessa gregaria Sars (1885), p. 120, pi. 21, figs. 8-17; pi. 22. 

 Thysanoessa gregaria, Holmes (1900), p. 230. 

 Thysanoessa gregaria, Holt and Tattersall (1905), p. 108. 

 Thysanoessa gregaria, Zimmer (1909), p. 20, figs. 32, 33, 34_ 

 Thysanoessa gregaria, Hansen (1911), p. 43; (1913), p. 174. 



The descriptions given by Sars, Holmes, Zimmer and Hansen are 

 very complete. In plate 1, figures 5 and 16, is shown the shape of 

 the front part of the head, and in plate 2, figure 24 is a part of the 

 first pleopod of the male, showing, from left to right, the spine-shaped, 

 terminal, proximal and lateral processes. The structure of the copu- 

 latory organs in our specimens agrees with the drawing given by 

 Hansen (1911, p. 44) and with that of Sars (1885, pi. 22, fig. 29). 

 Hansen states that these organs form the best specific characters, 

 especially in the structure of the proximal process. There is much 

 variation in the length and shape of the rostrum and in the length 

 and relative depth of the sixth abdominal segment. T. gregaria is 

 one of the species having the elongated second legs. 



The length is from 12 to 15 mm. 



Thysanoessa spinifera Holmes 



Thysanoessa spinifera Holmes (1900), p. 229, pi. 4, fig. 81. 

 Thysanoessa spinifera, Hansen (1911), p. 41. 



This species may be readily identified by the strong keel on the 

 upper surface of the fourth and fifth abdominal segments, each keel 

 ending in a long spine directed backwards. The corneal portion of 

 the eyes is not constricted as in gregaria. 



Our collections contained two females, each 15 mm. long. Holmes 

 gives the length as 30 mm. 



Genus Nematoscelis Sars 



Nematoscelis Sars (1885), p. 126. 

 Nematoscelis, Zimmer (1909), p. 16. 

 Nematoscelis, Hansen (1910), p. 106. 

 Nematoscelis, Plansen (1911), p. 47. 



The most characteristic mark of the genus is the greatly length- 

 ened and extremely slender second pair of legs (see pi. 2, fig. 35, and 

 Zimmer, 1909, figs. 24, 25). In some species the last joint only bears 

 bristles, in others the last joint and distal end of the preceding one 



