SANGUINOLITES MONENSIS. 155 



its dorsal slope is also more pronounced, and much more extensive; and the 

 gibbosity is much more oblique, duo to the much smaller amount of constriction in 

 S. tumida. 



Spathella tumida, sp. nov. Plate XXIII, figs. 5—7. 



Sanguinolites plicatus, M'Coy, pars, 1844, Synops. Carb. Foss. Ireland, p. 49, 



pi. x, fig. 3a. 



Specific Characters.— Shell of medium size, transversely oval, inequilateral, 

 regularly tumid. The anterior compression is small and only apparent near the 

 margin. Dorsal slope compressed, only slightly hollow, comparatively small. The 

 anterior end short, its border elliptical. The inferior margin gently convex, the 

 posterior margin obliquely truncate, nearly straight above, bluntly rounded below. 

 The hinge-line almost straight. The umbones tumid, incurved and somewhat 

 twisted forwards, slightly raised and placed about the junction of the anterior and 

 middle thirds of the valve. Escutcheon well developed, elongate. 



Interior. — Normal, but hinge-line not exposed. 



Exterior. — -The surface is ornamented with concentric folds and sulci, somewhat 

 oblique to the long axis of the shell. 



Localities. — England : the Carboniferous Limestone of Thorpe Cloud and 

 Castleton, Derbyshire. Ireland : (?) Bruckless, co. Donegal. 



Dimensions. — PI. XXIII, fig. 5, a right valve from Thorpe Cloud, measures — 

 Antero-posteriorly . . . .43 mm. 



Dorso-ventrally . . . .18 mm. 



From side to side (estimated) . . .14 mm. 



Observations. — The specimen figured by M'Coy (re-figured PI. XXIII, fig. 6) is 

 evidently distinct from Sanguinolites plicatus, Portlock sp., to which he referred 

 it. From the absence of oblique ridges I now refer the shell to Spathella under 

 the specific name of S. tumida. Several specimens of this shell have been 

 obtained at Thorpe Cloud and Castleton, which have enabled me to study many of 

 the characters of the species ; but unfortunately the hinge-plate cannot be com- 

 pletely seen. The shell is much less transverse and more gibbose than that of 

 S. cylindrica. 



Sanguinolites monensis, sp. nov. Plate XXIII, figs. 14 — 1G. 



Specific Characters. — Shell below medium size, transverse, narrow and suit- 

 cylindrical in front, inequilateral, compressed but expanded in the dorso- ventral 



