1914] Esterly: Schizopoda of the San Diego Region 13 



species the joint carries a strong spine at the distal end so disposed that, 

 with the end joint, a kind of grasping organ or chela is formed. The 

 eyes are large and more sharply constricted into two portions than 

 in Neynatoscelis, for example ; the difference in size between the npper 

 and lower segments is more marked also. In Nematoscelis the lower 

 part is either directed forward or the two parts lie in the same dorso- 

 ventral line but in Stylocheiron the lower part lies well posterior. In 

 the female (Hansen, 1911, p. 52) the endopodite of the fifth (sixth) 

 legs is 3- jointed, that of the sixth (seventh) pair 2- jointed. The 

 males always lack the inner ramns in the sixth (seventh) pair, while 

 in the fifth (sixth) pair it may be present, as in the female, or 

 lacking. 



Our material of Stylocheiron consists of two specimens. One is an 

 egg-bearing female in which both of the elongate legs are broken; the 

 other is an immature individual that belongs in all probability to 

 ^S*. maximum Hansen. The chelae closely resemble those shown by 

 Hansen (1910, pi. 16, fig. 6b) and the structure of the eyes and the 

 abdominal segments show that the immature specimen does not belong 

 to S. ahdreviatum (Hansen, 1910, p. 122). 



The larger specimen is 25 mm. long, the smaller about 12 mm. Since 

 the former lacks the very characteristic "chelipeds" and the other 

 is not mature it is unnecessary to deal farther with them. 



ORDER MYSIDACEA 



The principal characters of this order have already been men- 

 tioned. A very full discussion is given by Hansen (1910, pp. 4-11) 

 and beginning on p. 11 he presents a synopsis of the subfamilies and 

 tribes of the largest family, the Mysidae. The account of the order 

 and the synoptic keys for families given by Zimmer (1909, p. 28) 

 should be very useful; he considers the Mysidae on p. 43 and on 

 succeeding pages he gives keys for subfamilies and genera. 



Key to the Genera op the Mysidacea 



1. Eyes of the usual form (pi. 1, figs. 11, 17) 2 



1. Eyes reduced to plates, fused in the middle line, without pigments or facets 



(pi. 1, fig. 7) Pseudomma 



2. The outer ramus of the uropod consists of two joints Siriella 



2. The outer ramus of the uropod consists of one joint 3 



