144 CARBONIFEROUS LAMELLIBRANCHIATA. 



from above downward and backward. The postero-inferior angle almost a right 

 angle, the postero-snperior an obtuse angle. The hinge-line is almost straight. 

 The umbones are large, tumid, raised, incurved beaks, prosogyrous, and placed 

 in front of the centre of the hinge-line. The valves are regularly convex, the 

 dorsal slope well marked and concave. 



Interior. — Unknown. 



Exterior. — The surface is almost smooth, but irregularly distributed lines of 

 growth are to be distinguished. 



Dimensions. — PL XXIV, fig. 15, M'Coy's type, measures — 



Antero-posteriorly . . . .33 mm. 



Dorso-ventrally . . . .19 mm. 



Localities. — England : the Carboniferous Limestone of Castletou, Derbyshire. 

 Ireland : Carboniferous Limestone, Mullaghatinny, co. Tyrone. 



Observations. — The type of Axinus obovatus, M'Coy, is contained in the Griffith 

 Collection, Museum of Science and Art, Dublin, and I refignre it in Plate XXIV, 

 fig. 15. It is crushed and therefore flattened, and otherwise fairly well preserved. 

 One other specimen of the species has occurred to me from Castleton, a right 

 valve (PI. XXIV, fig. 14), which is not crushed and shows the deep dorsal slope. 



8. obovatus is more transverse and regularly oboA r ate than any other species of 

 the genus. 



Carbonioola Vinti, Kirkby, sp., 18(34. Plate XXV, figs. 18—20. 



? Ancylus Vinti, KirTcby, 1864. Trans. Tyneside Nat, Field Club, vol. vi (1864), 



p. 220. 

 Carbonicola Vinti, Iliad, 1899. Quart. Jouni. Geol. Soc, vol. lv, p. 367, pi. xxv, 



figs. 5—13. 



Specific Characters. — Shell very small, inequilateral, ovate, compressed. The 

 anterior end is broad, and its border is regularly rounded. The inferior border is 

 regularly but gently convex. The posterior border is narrowed by the approxima- 

 tion of the upper and lower margins, obliquely truncate from above downward and 

 backward, making a well-marked obtuse angle with the hinge-line above and an 

 acute angle with the inferior margin below. The hinge-line is arched, extended, 

 and depressed posteriorly. The umbones are small, tumid, slightly elevated, and 

 situated in the anterior fourth of the shell. 



The valves are regnlarly and gently convex for the anterior two-thirds, but 

 gradually compressed in the posterior third. 



Interior. — The muscle-scars appear to be normal. The hinge has not yet been 

 isolated. 



