ANTHRACOMYA PULCHRA. 115 
rapidly compressed into the hinge-line, so that this portion of the shell is slightly 
concave, and at times is crossed by obsolete radiating lines. 
Interior.—Normal; hinge like that of A. modiolaris, the details bemg very 
minute. 
Exterior—The surface is almost smooth, but there are very fine striz and 
lines of growth. Periostracum wrinkled. 
Dimensions.—A full-grown example from the Burnwood Ironstone, Golden 
Hill, measures— 
Antero-posteriorly : ‘ : . 23 mm. 
Dorso-ventrally : : : 5 ILil Taman, 
From side to side : . 9mm. 
Localities; —The Burnwood or Little-Mine Ironstone of North Staffordshire, 
Fenton, Golden Hill, Pitts Hill, and New Chapel. 
Observations —At Golden Hill (North-Staffordshire Coal-field), the Burnwood 
or Little-Mine Ironstone, as it is called in the Longton district of the same 
coal-field, consists of a finely laminated ironstone above, containing A. Adams ; but 
its lower part is much more homogeneous and not at all well stratified, and in this 
part of the bed A. pulchra is found with Naiadites carinata. At Fenton, however, 
the species does not seem to occur, though A. Adamsii is very common, and is nearly 
always found in a perfect state. I believe that this is the shell which Mr. Salter 
identified as A. pumila in his remarks on the paleontology of the North Staf- 
fordshire Coal-field (op. supra cit.), but on comparing it with the South Wales 
specimens the difference is very apparent; A. pulchra is much more convex. The 
oblique ridge is less angular than in A. pumila, Salter, or in A. Williamsoni, Brown, 
and the posterior end not expanded to so great an extent as in the Welsh shells. 
I figured two crushed specimens of this shell as A. pumila (op. supra cit.), the 
characteristic features being obliterated. I have never met with this species from 
any other seam or coal-field. It is very abundant and in a splendid state of 
preservation in all stages of growth in the bed stated. 
I have figured a series, Pl. XV, figs. 29—49, to show the change of shape 
resulting from growth. The absence of any marked expansion of the posterior 
end in the young is very apparent, room for the viscera being obtained by a much 
greater convexity of the shell posteriorly than obtains in most of the species of the 
genus, but later on in life the typical shape is always present. I have not figured 
any specimen showing the hinge. The details are very small, and it is difficult to 
get specimens altogether free from matrix; but from fragments I have seen I 
believe the hinge-apparatus to be identical with that of A. modiolaris. No casts 
have as yet been obtained. 
