258 
Mr. R. Etheridge, Jun., on a 
small Phyllopod in the Wardie-Shale group of the rocks in 
question. It is either a new and peculiar form of the 
genus Leaia, or, as Prof. T. Rupert Jones was at first in¬ 
clined to think, perhaps a species indicative of an undescribed 
genus. 
The genus Leaia has not been previously unnoticed, how¬ 
ever, in our Lower Carboniferous rocks. Many years ago 
the late Mr. J. W. Salter discovered a variety of the type 
species in the rocks of the Fifeshire coast, which was described 
by Prof. T. Rupert Jones as L. Leidyi , var. Salteriana. 
A form of Leaia was found in an ironstone nodule from 
the Wardie Shales at Wardie, near Edinburgh, by Mr. C. W. 
Peach ; and the discovery was noticed by Prof. Jones* * * § and 
Mr. Peach f. 
Leaia , notwithstanding its limited number of species, is 
now known to range from the uppermost part of the Old Red 
Sandstone (or lowest part of the Carboniferous ?) of Pennsyl¬ 
vania to the Coal-measures |, although, so far as I am aware, it 
has not yet been met with in the Carboniferous Limestone. 
The genus is described by Prof. Jones as possessing a mark¬ 
edly quadrate bivalved carapace, thin and horny, truncated 
and slightly curved behind, boldly rounded in front, and 
straight on the dorsal edge. The surface of the valves is con¬ 
centrically ridged with lines of growth, and ornamented with a 
delicate reticulation in the intermediate furrows. Each valve 
is crossed by two conspicuous ridges : one of these passes 
directly across the valve from a slight anterior umbo to the 
antero-ventral angle; the other and longer forms a diagonal 
to the postero-ventral angle, thus dividing each valve into 
three unequal triangular areas. The concentric ridges (pass¬ 
ing from one transverse ridge to the other) vary in their prox¬ 
imity one to another and in their relative strength of develop¬ 
ment. These are the characters derived from the type species 
and its varieties. 
The form described by Meek and Worthen as Leaia trica- 
rinata § leads us a step further, and overrides the foregoing 
description as to one point. It corresponds in all essential par¬ 
ticulars with the type species, but is said to possess a third 
carina or ridge, lying along the dorsal margin of each valve 
and enclosing what the authors term a “lanceolate corselet,” or 
* Geol. Mag. 1871, viii. p. 96. 
t Brit. Assoc. Report for 1871, pt. 2, p. 109. 
t Jones, Mon. Foss. Esther ice, p. 117, &c. 
§ Illinois Geol. Report, 1868, iii. p. 541 : Jones, Geol. Mag. 1870, vii. 
p. 219. 
