210 CARBONIFEROUS LAMELLIBRANCHIATA. 



latter species is founded upon a single valve, but both forms are from the same 

 locality and horizon, " Calc-schiste " of Tournai. 



Barrois has described one species of this genus from the Carboniferous beds of 

 the Asturias and Gallicia, Spain, under the name G. Halli, but this species seems 

 to me to be identical with that described by de Ryckholt and de Koninck. 



Ctenodonta sinuosa, <le Bychholt, sp., 1853. Plate XVJII, figs. 1 — G. 



Lkda sinuosa, de Ryckholt, 1853. Melanges Pal., pt. 2, p. 151, pi. xvii, figs. 5, G. 

 Ctenodonta sinuosa, Biysby, 1878. Thesaurus Devonieo-carboniferus, p. 303. 

 — Halli, Barrois, 1882. Recherches Terr, anciens des Asturias et 



de G-alice, p. 339, pi. xvii, figs. 2 a — c. 

 Tellinomya sinuosa, de Koninck, 1S85. Ann. Mus. Roy. d'Hist. Nat. Beige, 



torn, xi, p. 139, pi. xxv, figs. 24, 25 ; pi. xxvi, 

 figs. 22-29, and 42. 



Specific Characters. — Shell of moderate size, transversely ovate, moderately 

 convex, produced posteriorly. The anterior side comprises about one-third of the 

 valve, and is regularly swollen, much deeper in a dorso-ventral direction than the pos- 

 terior end, which is compressed, narrowed, and produced. The anterior border is 

 regularly rounded, passing with a continuous curve into the inferior, which is 

 convex, especially in front, and produced. The posterior border is very short, 

 bluntly pointed, narrowed by the approximation of the ventral border and the 

 hinge-line. The latter is very slightly arcuate, and produced posteriorly. The 

 umbones are small and inconspicuous, contiguous, not elevated, only limited in 

 front; elsewhere they are continuous with the general convexity of the valve. 

 They are situated at the junction of the anterior and middle thirds of the valve. 

 Commencing at the apex of the umbo a narrow ridge passes backwards, almost 

 parallel with the hinge-line, forming with that of the opposite valve a well-marked 

 escutcheon. The valve is regularly convex from before backwards, and above 

 downwards, the point of greatest convexity being midway between the umbo and 

 the ventral border. 



Interior. — The anterior adductor muscle-scar is round, large, deep, and 

 situated just within the margin at the anterior-superior angle. The posterior is 

 pear-shaped, situated within the posterior slope, remote from the border, with a 

 deep, elongate, narrow, accessory scar between it and the upper border. The 

 hinge-plate consists of an anterior set of about six teeth, triangular in shape, with 

 the apices directed backwards, and which gradually become smaller as they 

 approach the umbo ; the teeth in the posterior set are much more numerous, at 



