190 On Ancient Water-fleas of the [pe ote ero 
the probable family alliances of this palzeozoic genus, remarking that 
we find some of the characters of its carapace among the existing 
Bivalved Entomostraca, both of the Phyllopod and Lophyropod 
groups, whilst others of its peculiarities have not been traced. It 
is not well represented by any known recent form, but partakes of 
the characters of several. Without again treating in detail of the 
shape, muscle-spot, and eye-spot, I will here indicate by such a table 
as I used before, but somewhat improved, the points of resemblance 
between the carapace of members of the recent families of Entomo- 
straca and that of Leperditia (+ meaning strong resemblance or 
identity of structure; — showing a want of resemblance; and * a 
trace of likeness) :— 
OsTRACODA. PHYLLOPODA. 
: ; Cypri- | Entomo- Conchee-| Cythe- | ,. - 
Cypride. | Cytheridz.) qinadm, conchide. | ciadw. | rellidze, Limnadiade. 
Eye-tubercles .. 
Resemblance in outline .. * * * * * * * 
Muscle-scar: lucid spots + -- + + at ft JL 
vascular sinuses .. _ — _ = — = ae 
radiating marks .. = — _ —- | = _ = 
Situation of the eyes + + + rp | = *9? a 
* — — = — 
On a review of the facts of the case, it seems to me that the 
relationship of Leperditia is stronger with the Ostracods than with 
the Phyllopods, judging from the carapace alone; and I take this 
opportunity of stating my views. None of the recent Bivalved 
Entomostraca resemble it closely as to the carapace ; and though 
some young Limnadians present such an oudline in their valves, we 
must not count much on that circumstance, for the other features 
of the valves are different, and the mode of growth of the Limna- 
dian carapace is very different. Among the Entomostraca all the 
bivalves necessarily have the sub-central transverse muscle, with its 
scar on either valve. ‘This is indicated by some kind or other of 
“Jucid spots” in all; and certainly the associated vascular sinuses 
and. radii (branchial canals) seen in Leperditia have their strongest 
analogues in Limnetis among the Limnadians. To whatever extent 
this may be an essential character of the test, it cannot be of so 
much systematic importance as the relative situation of the eye of 
the animal, which in Leperditia the anterior tubercle indicates to 
have been upwards and forwards, as in the Ostracodans generally, 
whether they have in the valve an external indication of that organ 
(as in some Cypride) or not. 
Thus, in this ancient animal, as in others, we find characters 
associated together which in modern forms are to be looked for in 
separate genera and families. And if it be so with regard to the 
