72 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I3I 



as organs of feeding. The pleopods (E) and the uropods (F), on the 

 Other hand, appear to remain in an early stage of development repre- 

 sented by the simple, unsegmented biramous stage of the pereio- 

 pods (B). 



The swimming appendages of the anostracan branchiopods so regu- 

 larly have six mesal lobes (figs. 3 F, 27 A, B) and a movable terminal 



Fig. 28. — Development of the pereiopods and pleopods of Penacus set if cms (L.) 

 (from Heegaard, 1953). 



A, rudiments of pereiopods on thoracic segments of second protozoea. B, 

 pereiopod of third protozoea. C, pereiopod of second mysis instar. D, third 

 pereiopod of postmysis. E, second pleopod of young adult. F, uropod of post- 

 mysis. 



Bspd, basipodite ; Cxpd, coxopodite ; Endpd, endopodite ; Expd, exopodite ; 

 Prpds, pereiopod rudiments ; Prtpd, protopodite. 



lobe as to suggest that the six endites represent the first six segments 

 of a leg (coxopodite to propodite) and the independently musculated 

 apical lobe the dactylopodite. Yet, the sixth endite is commonly inter- 

 preted as the endopodite and the apical lobe as the exopodite. In the 

 notostracan Apus, however, the second maxilliped (fig. 27 C) is a 

 seven-segmented leg ending with a clawlike dactylopodite (Dactpd) 

 and having an endite on each of the other segments except the 

 ischiopodite. The first maxilliped of Apus (D) is somewhat simpli- 



