ABT. IS SYNOPSIS OF CALANOID CEUSTACEA MAESH 17 



endopod of the maxilliped is 4-segmented (pi. 9, fig. 3). All the 

 swimming feet are biramose, the exopods having three segments and 

 the endopods one. In all the feet the endopods bear five setae. In 

 the first foot the first and second segments of the exopods have each 

 two setae, one external and one internal ; the terminal segments bear 

 six setae. In the second (pi. 9, fig. 5), third, and fourth feet the 

 first and second segments of the exopods have spines externally in- 

 stead of setae as in the first foot; the terminal segilients have two 

 short spines on the external border, at the end a long spine with its 

 outer margin deeply serrate, and four setae on the inner border. 



The fifth feet of the female (pi. 10, fig. 4) are uniramose. The 

 first basipods are confluent; the second basipods are distinct; the 

 exopod is 2-segmented, the second segment armed at the tip and 

 sometimes on the sides with spines, which vary in number from three 

 to eight ; there are no endopods in mature forms. 



The fifth feet of the male (pi. 9, fig. 4) are uniramose and dis- 

 similar; the first basipods are confluent. The right foot consists of 

 the second basipod and an exopod of one segment, the exopod being 

 strongly flexed. The left foot consists of the second basipod and 

 au exopod of two segments ; the second basipod bears a long curved 

 process projecting from its inner border; a study of larval forms 

 shows that this process represents an endopod; the second segment 

 of the exopod is more or less sinuate on the inner margin and, in 

 all except E. chankensis^ armed with spines; in E. chankensis there 

 is a tuft of cilia at the tip. 



Occurrence. — With the exception of two species, E. haikalensis and 

 E. chankensis, which are found in Asia, the genus occurs only in 

 Xorth America. It is not commonly found much south of latitude 

 40° N. in America, and it extends north to Alaska. The three 

 American species appear to have a fairly restricted distribution — 

 E. lacustrls to the general region of the Great Lakes, going north 

 to Lake Winnipeg, E. nevadensis to the mountains of the Pacific 

 region, from central California to Alaska, and E. nordenskioldi to 

 the Atlantic coast from Newfoundland to North Carolina. 



KETSr TO THE SPECIES OF EPISCHURA 



1. Segments 2, 3, and 5 of male abdomen armed with projecting 



processes 2 



Only fifth abdominal segment of male armed with projecting 

 processes 4 



2. Female abdomen bent to right, and external furcal setae much 



broader than others lacustris Forbes 



Female abdomen straight or nearly so, and all furcal setae 



approximately same width 3 



] 55089—33 2 



