CARBONICOLA TURGIDA. 67 



Caebonicola tubgida, M'Coy. British Palseoz. Foss., 1854, p. 516. 

 Antheacosia ovalis, Salter. Memoirs G-eol. Surv. Great Britain, Iron Ores, &c, 



1861, pt. 3, p. 226, pi. ii, figs. 22, 22 a. 

 — centealis, Ward. Transact. North Staffordsh. Instit. Min. Mech. 



Engineers, vol. x, 1890, p. 126, pi. 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 V _sna P e< ^ trench. 

 Valves very tumid, more so anteriorly, becoming gradually flattened posteriorly, 

 marked with fine concentric strias and lines of growth, often slightly oblique to the 

 long axis of the shell, also very fine radiating strise. 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 inner 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 . .37 mm. 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, 

 G-antre, 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 



