OSTRACODA. 



115 



Though we have thought it desirable to give these brief generic diagnoses, inserting 

 only such characters as may be derived from the formation of the carapace (this being the 

 only part of the animal available to the palaeontologist) ; it should, nevertheless, be 

 clearly understood that the really important generic distinctions are, in almost all cases, 

 based upon the structure of the internal organs, chiefly, indeed, on the formation of the 

 limbs, mouth-apparatus, and sexual organs. Yet, in the majority of cases, these deep- 

 seated peculiarities coincide so remarkably with a particular form of shell that there need 

 usually be no difficulty in assigning the fossil remains met with in the Tertiary and Post- 

 tertiary strata to their proper genera. Amongst the Entomostraca of the Palseozoic 

 formations, however, we meet with types of shell-structure far removed from those of 

 recent times and can only vaguely conjecture as to their relations. 



From the foregoing Table we have excluded altogether the family Conchoeciadse, the 

 delicate valves of which have not been found (nor, indeed, are they likely ever to be 

 found) in any geological formation. The exclusively Palseozoic genera are also omitted, 

 as well as the recent genus Meter odesmus, which has not been met with except in the 

 Chinese seas, and seems to be allied to the Carboniferous genus Entomoconchus. 



M 



OSTRACODA — Synopsis of Genera based upon the anaiomical characters of the animal. 



1 



P4 



o 

 o 



<i) 



xn 



Possessing a bran- 

 chial appendage ; 

 palp subcorneal, in- 

 distinctly jointed, 

 ending in three 

 setae. 



Second joint of 

 lower antenna 



r, 



destitute of a bran- 

 chial appendage. 

 Palp 



bearing a brash of setsB. /'well developed, terminating in two sti'Qng") p • ^ 



Setse of the upper an- \ cm-ved claws ^ VP • 



tennae very long. Post- 1 



abdominal rami (^rudimentary, setiform Cypridopsis. 



Foiamocypris. 



Paracypris. 



. Aglaia. 



[ Notod/)-omas. 



Candona. 

 Pontocypris. 



without a brush of setaj.r™^"^'''*^'"^ 



tetn8efery^shOT<^%n«t^ well-developed, terminating in") alike 

 abdominal rami 



tennae very short. Post- ; , , " j i •£<• j. C 



----•'■ I two strong curved claws. J* irst > 



l^and second pairs of feet 



J dissimilar 



subconical, indistinctly ( ■ S i "m 



iointed. Setae of lower )^"^^^^1^^^- ^^^ 



long, reaching beyond the apex of the ter 



eyes 



r 



distinctly 

 jointed, 

 subpedi- 

 l^form 



3-jointed ; 



upper 



antennae 



(..altogether wanting. One eye 

 felongated, 7-jointed, armed with long setse 



■{ short and robust ; 5-jointed ; in the female"^ 

 I shortly setose, in the male provided with a > Argilloecia, 

 l^f ew long setae . . . . . ■) 



4-jointed ; up-"^ largely developed, terminating in save- '} j^^^:^ja^ 

 per antennae ral long setae ...... j 



shortly setose. )■ 



Postabdominal | rudimentary Macrocypris. 



l^rami J 

 Ajiimal unknown Goniocypris. 



With this genus we incorporate Cypria (Zenker) and Chlamydotheca (Saussure). 



