1914] Esterhj: Schizopoda of the San Diego Region 3 



of the carapace at the lower edge may be smooth or carry one (pi. 1, 

 fig. 14) or two (not more) small forward-pointing teeth. The seventh 

 and eighth pairs of legs are nearly always more or less reduced, the 

 eighth pair especially showing a tendency toward retrogression. The 

 second to eighth pairs of legs carry gills, and these are retained on 

 the last two pairs irrespective of the amount of reduction undergone 

 by the appendages. The gills on the anterior legs have but one main 

 branch while the posterior ones have several. The pleopods are well 

 developed in both sexes and serve as swimming feet; the inner rami 

 of the first and second pairs function in the males as copulatory or- 

 gans. These structures are of great systematic importance and de- 

 tailed accounts of them will be found in the papers by Hansen (1910, 

 pp. 79, 80; 1911). He states (1910, p. 79) that the endopod of the 

 first abdominal appendage (using the genus Thysanopoda as the type) 

 is divided into three large lobes, the "inner," "median" and 

 "setiferous;" an "auxiliary" lobe may be present between the 

 setiferous and median lobes or attached to the base of the inner 

 margin of the former. The setiferous lobe and the stalk by which 

 the endopod is attached to the basipodite are regarded as the inner 

 ramus proper, while the other lobes are outgrowths of the inner 

 portion of the endopodite in this sense. In Thysanopoda (which does 

 not occur in our collections) the inner lobe carries three processes, 

 the more median one designated as the "spine-shaped," the "term- 

 inal" process on the end of the lobe between the bases of the spine- 

 shaped process and the "proximal" process; the latter is the outer 

 one of the three of the inner lobe. The median lobe is longer than 

 the inner and carries the "lateral" process, which is strongly hooked 

 in Thysanopoda and Euphausia. 



From this typical condition there are marked difi^erences in the 

 number and shape of the processes, and these are of much value in the 

 separation of genera and species. As Hansen states (1910, p. 79) 

 the inner plate with its lobes is rolled up from the inner side. Its 

 dissection and proper arrangement is often rather difficult. 



Phosphorescent organs are characteristic of the Euphausiidae ; 

 the organs are lens-shaped and one is normally found on each eye 

 stalk, a pair on the base of the second and seventh legs and one under 

 each of the first four segments of the abdomen. 



The Mysidacea, in contrast to the Euphausiacea, may not have 

 gills on the legs, or, if present, they are covered by the carapace; 

 the telson (pi. 2, fig. 21) lacks the subapical appendage. Ortmann 



