259 
small and new Phyllopod Crustacean. 
u lanceolate false area.” Meek and Worthen, however, admit 
that this peculiarity is not always to be seen, but only in those 
individuals which have not undergone pressure. 
On this point Prof. Rupert Jones observes, “ Messrs. Meek 
and Worthen have shown that in some species of Leaia there 
is evidently a third (dorsal) carina on each valve, bounding a 
dorsal depression (their Maneolate false area’), along the 
bottom of which is the hinge-line. In compressed specimens 
this is not distinguishable; and whether or no it is present in 
all they leave an open question He adds, “As to outline 
and proportions, the many individuals on the shales found by 
Mr. W. Adams in South Wales comprise all the forms yet 
figured by Lea, Dawson, Meek and Worthen, and myself, 
and may be due to differences in age or sex, or conditions of 
preservation.It is, of course, probable that different 
4 species ’ did exist, and are represented amongst the different 
forms found in distant countries ; but we still wait for further 
and decided evidences of specific characterization.” 
The sum of this evidence appears to be that, if further re¬ 
searches bear out the characters originally assigued to Leaia , 
as typified by Cypricardia Leidyi , Lea, and if the ridges have 
an important physiological meaning, then Meek and Worthen’s 
species L. tricarinata should be considered generically dis¬ 
tinct, provided the third carina on each valve, and the 
“ lanceolate false area ” enclosed thereby, are constant and 
well-defined characters, as, indeed, there does not appear any 
reason to doubt from the evidence of Meek and Worthen’s 
figures B 2 and B 3. 
On this point Prof. Jones has favoured me with the follow¬ 
ing remarks :—“ It is possible, however, that if the two 
valves of L. tricarinata be opened out, in apposition, by their 
dorsal edges only, these particular dorsal carina may become 
obscured by pressure and imbedment; whereas if preserved 
in a good state with closed valves, and seen on the dorsal 
edge (as in Meek and Worthen’s fig. B 3), the carapace then 
clearly shows the above-mentioned dorsal carina and the 
intervening elongate dorsal lunette. Certainly none of the 
published figures of open pairs of valves give any indication 
of the lanceolate corselet; and, unfortunately, L. tricarinata 
does not appear to have occurred in the opened-out position, 
so as to show its behaviour under pressure. 
“ One of the published species which is figured in the ex¬ 
panded condition of the valves is Leaia Klieveriana , Goldcn- 
* Pror. Nat.-Ilist. Soc. Cardiff, 1809, ii. p. 117; Geol. Map-. 1870, vii. 
p. 219. 
