1914.] NATURAL SCIENCES OF PHILADELPHIA. 31 



These plates are smooth on the fifteenth and sixteenth segments, 

 but on the seventeenth (PI. I, fig. 7) the plate is coarsely serrate 

 from the base of the segment to the insertion point of the middle 

 seta; from thence to the end minutely serrated as in C. albidus. 

 This plate projects somewhat beyond the end of the seventeenth 

 segment. 



The second antennae (PI. I, fig. 5) are unusually long. The third 

 segment is the longest of the four — a distinguishing difference between 

 this and the following form. The swimming feet are armed as follows : 



First pair — outer ramus, four spines, four setae; inner ramus, one 



seta, one spine, four setae. 

 Second pair — -outer ramus, four spines, five setae; inner ramus, one 



seta, one spine, four setae. 

 Third pair — like second. 

 Fourth pair — outer ramus, three spines, five setae; inner ramus, 



three spines, two setae. 



Marsh has noted that "the larger of the two terminal spines of the 

 endopodite of the fourth foot, instead of being serrated on its edges 

 as is customary in all the spines of the swimming feet, is beset on its 

 inner margin with long, rather irregular teeth. " I find this character 

 present in the local specimens, though the "irregular teeth" do not 

 extend to the tip of the spine on its inner margin. There are but 

 five or six of these long serrations at the middle of the inner margin, 

 thence to the tip of the spine the serrations are normal. Schmeil 

 notes that the lamella which connects the basal segments of the 

 fourth pair of swimming feet is ornamented by a fringe of long hairs. 

 This is found also in C. albidus, and is therefore hardly a distinctive 

 character of C. fuscus. In all the specimens that I have examined, 

 these "hairs" are very coarse, resembling rather long serrations. 

 There is a very noticeable characteristic in the lamella between the 

 basal joints of the thij'd pair of swimming feet. There are two very 

 minute rows of blunt spinules extending transversely across the 

 lamella. The upper row is broken in the middle. In the following 

 species this character is very different. 



The fifth foot is practically identical with that of the following 

 species. Miss Byrnes states that the basal segment of the rudiment- 

 ary fifth foot in ^'coronatus" (= C fuscus) is conspicuously short. 

 Schmeil finds no such difference. Among all the representatives 

 of C. fuscus that I have compared with C. albidus, I have found 

 only very slight differences in the lengths of the basal segments of 

 the fifth feet. The apparent difference in length may often be 



