388 GEOLOGICAL SURVEY OF THE TEREITOEIES. 



the genital pore of the male Limnadiadce and the Apoclidce, together with 

 the gonopoda of the male Branchipodida;, as indicating the line dividing 

 the thorax (baenosome) from the abdomen (urosome). 



In the Limnadiadce the female btenopods are remarkably uniform in 

 appearance ; in the males, however, the first pair (Limnetis) and in 

 JEstheria and Idmnadia the first two pairs have the fourth to sixth 

 eudites transformed into a grasping or hand-like extremity, whose 

 structure is very interesting. 



We will first describe the thoracic foot of the female, as it is simpler 

 in structure than in the male. As seen on Plate I, figs. 3 and 4, Plate II, 

 fig\ 1, in Limnetis the axis or trunk of the limb is quite indefinite in 

 outline, and is entirely subordinate in size and difierentiation to the 

 lobular outgrowths,, the endites and exites.* In this respect the Li m- 

 nadiad leg closely resembles the Cladocerous appendage, and in this 

 characteristic the appendages seem clearly enough a direct bequest of 

 the lower Branchioi)ods {Gladocera and Ostracoda). Considering first 

 the inner or sternal series of lobes, i. e., the endites, we can easily make 

 out six endites, the normal number for all Phyllopoda. (See fig. 26 in 

 text.) The first endite (fig. 1 I', in other figures cl) we have called the 

 coxal lobe {cl); it is the '■'■maxillarfortsatz'''' of Grube, and corresponds, 

 or is homologous with, the first foot-lohe of Apiis of Gerstaecker, or the 

 gnathohase of Lankester (Q.J. M. S., p. 348, 1881). It would be difficult, 

 and a straining of homologies, to compare this with the coxopodite 

 of a Decapod, as these endites are characteristic of the Branchiopoda, 

 and do not exist in a completely jointed appendage, such as those of the 

 Malacostracous or Copepodous Crustacea. 



The gnathobase is large, long, and well developed in Limnetis ,- its 

 long, sharp, stout spines nearly meeting those of its fellow opposite, 

 over the sternal groove of the under side of the body, and serving ad- 

 mirably as maxilla-like organs for the retention of the food, and for 

 passing it forwards to be crushed between the mandibular teeth guard- 

 ing the mouth. 



The second and third endites are broad, short, unequal lobes, the 

 second the longer, and provided with long, delicate setulose setse. The 

 fourth endite assimilates in form to the fifth and sixth, being long and 

 slender, though the setiferous edge is as extended as in the second endite. 

 The fifth and sixth endites (P, l^) are each very long and slender, and 

 semi-jointed, a seta arising from each pseudo-joint. 



The exite in this family is much more differentiated than in the Apodidm 

 or the Branchipodidce, and the flabellum performs a variety of work 

 besides respiration. In Limnetis the exite is divided into three portions ; 

 the gill, which is oval, pear-shaped, and moderately large, while the fla- 

 bellum is differentiated into a dorsal or upper very large and broad 

 (Plate II, fig. 1; Plate XXVII, fig. 3), or rather narrow (L. mucronattis) 

 portion (br'), and a lower slender part {Ir") which assimilates in form, 

 and probably in function to the fifth and sixth endites of the same appen- 

 dage. 



In Estlieria and also in Eulimnadia the relations of the dorsal division 

 of the flabellum (which is narrow and slender) to the gill is seen in 

 Plate V, fig. 1, and also in Plate XXIV, figs. 9 and 10. Some of those at 

 the middle of the body serve to hold the eggs in place, for which function 

 they are well qualified by reason of their great length, since they nearly 

 meet over the back of the animal, and their long setae seem to hold the 



* The terms endite and exite were first proposed by Professor Lankester iu liis memoir 

 on Apug, Q. J, M. S., I'fSl. We liave extended the term to the outer lobes of the feet 

 of Phyllopods in general. 



