146 CARBONIFEROUS LAMELLIBRANCHIATA. 



the horizon of this fossil, C. Vinti occurring in this coalfield about the middle of the 

 zone of Anthracomya Phillipsii. 



Anthracomya calctfera, Hind, 1899. Plate XXV, figs. 21 — 23. 



Anthracomya calcipeea, Hind, 1899. Quart. Jouru. Geol. Soc, vol. lv, p. 365. 



Specific Characters. — Shell small transversely, modioliform, very inequilateral, 

 gibbose, expanded and flattened posteriorly, oblique. The anterior end is very 

 short, and narrower than the rest of the shell, and its border is elliptically curved. 

 The inferior border is produced downward and backward, and is almost straight, sub- 

 parallel with the superior border. The posterior border is comparatively lengthened 

 obliquely, truncate from above downward and backward, and is straight for the 

 greater part of its extent, but joins the inferior border at a somewhat rounded 

 angle. 



The hinge-line is straight, much shorter than the inferior border, and the 

 posterior superior angle is well marked and obtuse. The umbones are small, 

 pointed, incurved, and contiguous, placed in the anterior quarter of the shell. 



Passing downward and backward from the umbo towards the posterior inferior 

 angle is a well-marked, bluntly rounded fold, in front of which the valve is 

 obliquely compressed, and posterior to this fold the valve is rapidly compressed 

 and expanded to form the dorsal slope. 



Interior. — Hinge edentulous. Muscle-scars normal. Pallial line entire, remote 

 from the margin. 



Exterior. — The shell appears to be almost smooth, but under the microscope 

 faint concentric lines of growth are to be observed. Periostracum wrinkled. 

 Ligament external, small, lodged in a narrow groove. 



Dimensions. — PI. XXV, fig. 21, measures : — 



Antero-posteriorly . . . .6 mm. 



Dorso-ventrally . . . .3 mm. 



Elevation of valve . . . .1 mm. 



Localities. — The Upper Coal Measures of the North Staffordshire Coalfield. 

 A bed of freshwater limestone at Highfield marl-pit, Etruria, and excavation for 

 telegraph-posts, roadside, Bradwell ; marl-pit east of Cocknage Hill ; railway 

 cutting, Florence Colliery ; road cutting, from Trentham to Whitmore, close to 

 Butterton New Farm ; Newcastle-under-Lyme railway- cutting ; Etruria, road- 

 cutting ; quarries near Longport Station ; marl-pit, Richmond Hill, Stoke-on- 

 Trent ; Upper Coal Measures, Slade Lane, Fallowfield, Manchester coal-field. 



Observations. — This species is much more elongate, less oblique, and attains a 



