ANTHRA.COM YA 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 being very 

 minute. 



Exterior. — The surface is almost smooth, but there are very fine striae and 

 lines of growth. Periostracum wrinkled. 



Dimensions. — A full-grown example from the Burnwood Ironstone, Golden 

 Hill, measures — 



Antero-posteriorly . . . .23 mm. 



Dorso-ventrally . . . .11 mm. 



From side to side . . . .9 mm. 



_ 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. Adamsii ; 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 palasontology 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 J.. 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 X 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, PI. 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. 



