DAVIDSON — PAL/EONTOLOGICAL NOTES ON THE BRAOHIOPODA. 115 
EXPLANATION OF THE PLATES. 
Plate III. 
Fig. 1. Prodiicfa (jigantca, Martin. Interior of the ventral valve, from wliich a 
portion of the beak lias been removed so as to exl»il)it the 
unibonal cavity. A and C, adductor or occlusor ; R, cardinal 
or divaricator muscular impressions. L, cavity occupied by 
the spiral arms. 
gigantca, interior of the dorsal valve. J, cardinal process. 
A, adductor or occlusor muscular impressions. W, pro- 
jections, to which Mr. S. P. Woodward supposes the oral arms 
to have been attached ( /)• X, reniform impressions. Z, 
eminences corresponding to the hollows L in the ventral 
valve. 
These two drawings are taken from valves belonging to the 
same individual, which was obtained from the Carlioniferous 
Limestone of jlangollen, and is in the Museum of Practical 
Geology. It is one of the most instructive specimens which 
I have hitherto examined. The cardinal process was so 
much imbedded in the matrix that it could not be developed, 
so the deficiency was completed from a specimen in the 
British Museum. 
gigantea. Part of the hinge-line and upper portion of the car- 
dinal process, from a specimen in the British Museum. 
gigantea. Ideal section of both valves (slightly unproved), 
from the figm-e published by Mr. S. P. Woodward, at p. 233 
of his " Manual of the Mollusca." The letters refer to the 
same parts in the other specimens. 
semireticxdata, Martin. A fragment of the dorsal valve 
(enlarged), to show the beautifully marked adductor or 
occlusor muscular impressions (A), the ])rojections W, and 
the commencement of the reniform impressions. From 
Redesdale, in Northumberland ; in the Museum of Practical 
Geology. The cardinal process J, and the septum S, which 
are wanting or imperfect in the Survey specimen, have been 
correctly drawn from a similar but more complete example in 
the collection of Mr. Reed, of York. 
longinpina, Sow. ; from the Carboniferous shale of Karova 
(Russia), now in the Imperial Museum of Vienna, here given 
to show the great length of the spines. I am indebted to my 
friend Professor Suess, of Vienna, for this interesting di-awing. 
7. Cliondcs comoides, var. (?) {Producta hemisphcerica, Sow., according to 
Professor de Koninck.) A fragment exemplifying the great 
disproportionate thickness of the valves. B ventral, G 
dorsal valve. Along the weathered section of the ventral 
valve may be distinctly traced successive layers of shell, also 
small pits (K) along the cardinal edge, which were no doubt 
the tubular bases of broken spines. E, area. 
This specimen is from Ticlenham Chase (Gloucestershire), 
near Chepstow, in the collection of Mr. W. G. W. Ormerod. 
Plate IV. 
Figs. I, 2. Producta proloscidca, de Verneuil. From the Carboniferous Limestone 
of Vise, in Belgium : to show the tubuliform prolongations of 
the ventral valve. (These two drawings are taken from 
Professor de Koninck's Jlonogi'aph of the Genera Productus 
and Chonetes.) 
I 2 
