CARBONICOLA TURGIDA. 67 
CarBonicoLa TuRGIDA, M*Coy. British Palwoz. Foss., 1854, p. 516. 
ANTHRACOSIA OvALIs, Salter. Memoirs Geol. Surv. Great Britain, Iron Ores, &c., 
1861, pt. 3, p. 226, pl. ii, figs. 22, 22 a. 
a CENTRALIS, Ward. Transact. North Staffordsh. Instit. Min. Mech. 
Engineers, vol. x, 1890, p. 126, pl. i, fig. 16. 
Specific Characters.—Shell obliquely and obtusely oblong, very gibbous. 
The anterior end, situated below the level of the umbones, has a rounded anterior 
superior angle and an obtusely rounded border, passing by a gradual curve into 
the inferior border. The anterior part of the shell is small and compressed at the 
border, but swelling rapidly. The posterior end forms the greater part (about 
two-thirds) of the shell, and it becomes compressed above into the hinge-line and 
border. The posterior border is obliquely truncate with an obtuse angle. Ventral 
margin nearly straight. Hinge-line straight, about half the total length of the 
shell, oblique to the long axis of shell. Umbones situated about the centre of the 
hinge-line, large, obtuse, contiguous. Lunule elongate and narrow. Ligament 
external and short. The edges of the valves posterior to the ligament are bevelled 
at the expense of the upper border, forming an elongated \-shaped trench. 
Valves very tumid, more so anteriorly, becoming gradually flattened posteriorly, 
marked with fine concentric striz and lines of growth, often slightly oblique to the 
long axis of the shell, also very fine radiating striz. Interior very smooth. Muscle- 
scars: anterior-adductor scar circular and shallow, almost marginal; accessory 
pedal-scar above it. The posterior-adductor scar is ovately triangular, situated 
high up near the posterior superior angle of the shell. In the right valve the 
lower edge of the anterior portion of the hinge-plate is bevelled and facetted at 
the expense of its lower border, and above this is a slight horizontal ridge, which 
is the imner edge of the lunule. The lunule terminates in a ridge directed 
obliquely backwards and downwards, which is the cardinal tooth, and behind it is 
a pit for the reception of the cardinal tooth of the left valve. Posterior to this 
pit the hinge-plate is thickened into a boss, forming a second cardinal tooth. 
The rest of the hinge-plate is flat and smooth. 
Dimensions : Scotch specimen. 
Antero-posteriorly —. . 37mm. 43 mm. 
Dorso-ventrally : . 23 mm. 30 mm. 
Laterally . : - ‘18 mm. 20 mm. 
Localities—England : Stubbs’ Mine, Bardsley, Coalbrookdale. Grain’s Iron- 
stone, Farthing Lane, Dudley. Roof of the Moss Seam, North Staffordshire. 
Stanley Main and Shale Coal, Wakefield. Wales: Two feet above bottom vein, 
Gantre, Ebbw Vale, South Wales. Scotland: Dallmellington, Lurgar. Splint 
Coal, Wishaw Coal-measures. Upper Coal-measures, Cambuslang and Shettleston. 
Observations.—Captain Brown, who first described this form, gave two very 
