4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 8o 



tional segment should be recognized in the unbranched base of the 

 typical crustacean limb, and he recently (1925) holds to the possibility 

 that in a primitive state the crustacean limb was uniramous. He 

 states : " But it seems to me impossible to deny the possibility that 

 the exopod may be anologous with the epipod, and if so the primitive 

 appendage is uniramous." Hansen's contention that the basal or un- 

 divided part of a crustacean limb should be considered as three- 

 segmented instead of two-segmented is recently criticized by Bor- 

 radaile (1926) who states in his paper: "From the foregoing con- 

 siderations it is evident that the recognition of a three-segmented 

 protopodite in the Crustacea is purely empirical, for the actual third 

 segment is not homologous in all cases, being sometimes the third 

 segment of the primary series, sometimes compounded of the third 

 and fourth, sometimes the fourth alone, and probably in a few in- 

 stances compounded of the fourth and fifth, the actual second segment 

 in the latter two cases being compounded of the primary second and 

 third." 



According to Hansen (1925) the crustacean limb is composed of 

 eight true segments which he names as follows from the body : Prae- 

 coxa, coxa, basis, ischium, merus, carpus, propodus and dactylus. 

 If the old terminology were employed these would be: Pleuropodite, 

 coxopodite, basipodite, ischiopodite, meropodite, carpopodite, propo- 

 dite and dactylopodite. 



THE PRIMITIVE ARACHNID LEG 



Because the ancient group Arachnida has apparently evolved from 

 extinct types of the same sort as those that gave rise to the Crustacea, 

 it is apparent that a study of the appendages of the more generalized 

 arachnid groups should throw light on the controversy in regard to 

 the leg type for the primitive Crustacea. In working on the homology 

 of arachnid legs the writer follows Hansen's interpretation of the 

 Crustacean leg by calling the first segment in the generalized leg the 

 subcoxa. 



LEGS OF SOLPUGIDA 



The Solpugida, or sun spiders, have long been considered as being 

 one of the most generalized of the arachnid groups. This is due 

 particularly to the fact that in this group some of the cephalothoracic 

 segments remain free and movable. Much research has been done 

 on the body segmentation in the solpugids and on the morphology 

 of certain specialized organs. The legs, however, have not attracted 

 the attention that they deserve, although it has long been known that 



