164 



ESTHER F. BYRNES. 



throughout tJie group, but the ten-jointed forms vary considerably 

 within the group, occasionally combining three-jointed rami with 

 a two-jointed fifth foot, and occasionally two-jointed rami with a 

 one-jointed fifth foot. 



According to Herrick's classification of the Cyclopidae, there 

 is but one species having ten-jointed antennae, /. c\, C. pJialcratus, 

 which may combine either ten- or eleven-, usually eleven-jointed, 

 antennae ivith three-jointed rami in the shimming feet, and with a 

 one-jointed fifth foot. I have found this combination in a single 

 case, and the antennae contained each eleven segments. Herrick 

 gives only the formula for the fourth foot of C. plialcratus, with 

 which the above form also agrees. The entire armature of the 

 terminal joints of the four swimming feet in the Cold Spring 

 Harbor form is shown below. 



First Foot. 



Outer Ramus. Inner Ramus. 



3 outer spines. I outer seta. 



I apical spine. I apical spine. 



I apical seta. I apical seta. 



3 inner setae. 3 inner setae. 



Thiid Foot. 



Outer Ratnns. Inner Ramus. 



3 outer spines. I outer seta. 



I apical spine. I apical spine. 



I apical seta. I apical spine. 



Second Foot. 

 Outer Ramus. Inner Ramus. 



3 outer spines. I outer seta. 



I apical spine. I apical spine. 



I apical seta. I apical seta. 



4 inner setae. 3 inner setae. 



Fourth Foot. 

 Outer Ramus. Inner Ramus 



1 outer seta. 



2 apical spines. 



4 inner setae. 



3 inner setae. 



2 outer spines. 

 I apical spine. 

 I apical seta. 

 4 inner setae. 



2 inner setse. 



The length of the antenna in C. phaleratus as compared with 

 the cephalothorax is short, whereas in the Cold Spring Harbor 

 form the antennae are relatively long, extending nearly to the 

 second thoracic segment. Moreover, in a single instance the 

 long second joint of the antenna showed a light, transverse band 

 near its proximal margin, suggesting the characteristically short 

 second segment of the eleven-jointed antenna. 



The chief characteristics of the cy clops with the eleven-jointed 

 antenna are three-jointed rami in the swimming feet combined with 

 a two-jointed fifth foot (Fig. 4). 



Herrick recognizes three species having eleven antennal seg- 

 ments ; one of these is a European form of marked peculiarity ; 

 a second is C. diaphranus, whose species-characteristics are 

 eleven-jointed antennce, two-jointed rami in the swimming feet, and 

 a one-jointed fifth foot, witJi a long seta and one short spine. 



