DAVIDSON PAL^ONTOLOGICAL NOTES ON THE BRACHIOPODA. 115 



EXPLANATION OF THE PLATES. 

 Plate III. 



'ig. 1. Pvoducta gigantea, Martin. Interior of tlie ventral valve, from which a 

 portion of the beak has been removed so as to exhibit the 

 umbonal cavity. A and C, adductor or occlusor ; R, cardinal 

 or divaricator muscular impressions. L, cavity occupied by 

 the spiral arms. 



gigantea, 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 Carboniferous 

 Limestone of Llangollen, 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. Partjof 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 improved), 

 from the figure 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. 

 semireticulata, Martin. A fragment of the dorsal valve 

 (enlarged), to show the beautifully marked adductor or 

 occlusor muscular impressions (A), the projections 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 Sm-vey specimen, have been 

 correctly drawn from a similar but more complete example in 

 . the collection of Mr. Reed, of York. 



longispina, 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 drawing. 

 7. CJionetes conioidcs, YQi. (!) {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 Tidenham Chase (Gloucestershire), 

 near Chepstow, in the collection of Mr. W. G. W. Ormerod. 



Plate IV. 



Figs. 1, 2. Producta prohoscidca, 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 Monograph of the Genera Productus 

 and Chonetes.) 



I 2 



