438 BRITISH PALAZOZOIC FOSSILS. [Bracuropopa. 
very deep acutely angular sulci, rather more than one half of the front margin and one lateral margin elevated 
much above the level of the right lateral margin, and its five or six ridges, Entering valve moderately gibbous ; 
profile regularly and gently arched, so that its depth is greatest in the middle; middle and left side more tumid 
than the right side, which falls with the corresponding depression in the margin; lateral ridges gradually and 
slightly smaller than the middle ones; beak rather prominent, obtuse. Receiving valve slightly unsymmetrical, 
the right half or rather less being manifestly more tumid, and longer than the middle and left side; beak large, 
prominent, only slightly incurved ; profile with the greatest depth rather nearer the beak than the front margin, 
but regularly arched towards both ends; cardinal area high, flat, triangular. Surface closely reticulo-punctate 
under a strong lens. Length seven lines, proportional width 7, length of entering valve ;;,, depth of both 
valves together *. 
I have not perfectly seen the spires in this species, but from the large, flat, cardinal area, and punctured 
shell-tissue, I have little doubt of the genus. 
Position and Locality —Rare in the lower carboniferous limestone of Derbyshire. 
SPIRIGERINA? RADIALIS (Phill. Sp.) 
Ref. and Syn. = Terebratula id. Phill. Geol. York. Vol. IT. t. 12. f. 40 and 41. 
Desc.—Longitudinally broad-ovate ; greatest width about the middle of the length; front and anterior 
lateral margins forming parts of one semicircular curve ; posterior lateral margins converging to the beak, at 
an angle of about 80°; lateral and front margins in one plane, without trace of mesial sinus ; valves almost 
equally convex. Entering yalve slightly and evenly convex, longitudinally ovate ; beak small, prominent; sur- 
face radiated with from fourteen to sixteen very strong, simple, rounded, subequal ridges, continued perfectly 
simple to the apex of the beak; intervening sulci very deep, angular. Receiving valve slightly and evenly 
conyex; profile regularly arched, greatest depth about the middle; beak very prominent, slightly incurved ; 
eardinal area flat, triangular (no straight hinge-line) ; deltidium bipartite; foramen near the apex. Surface 
smooth to the naked eye, granulo-punctate under a strong lens, Length of small specimen two and half lines, 
proportional width “, length of entering valve +, depth of both valves ;;;. 
(Professor Phillips figures a specimen five lines long, in which the proportional depth of both valves 
together is *). The bipartite deltidium beneath the foramen in the flat area under the beak, and the coarsely- 
punctured tissue, as in the S. reticularis and 8. desquamata, leave little doubt on my mind of the true genus of 
this shell, although I have not yet seen the spires. 
Position and Locality —Rare in the carboniferous limestone of Derbyshire. 
7th Family. RHYNCHONELLIDZ. See page 199. 
Genus. HEMITHYRIS. See page 199. 
HeEMITHYRIS ACUMINATA (Mart. Sp.) See page 380. 
Ist Var. acuminata (Martin Sp.) See page 381. 
Position and Locality—V ery common in the main, grey, or lower, carboniferous limestone of Derbyshire ; 
in several varieties ; similar specimens very common in carboniferous limestone of Malham Moor. 
2nd Var. PLATYLOBA (Sow.) See page 381. 
Position and Locality Common in the carboniferous limestone of Derbyshire. 
3rd Var. pPuGNus (Sow.) See page 381. 
Position and Locality—Common in the carboniferous limestone of Derbyshire ; common in the dark lower 
earboniferous limestone of Isle of Man; common in the lower carboniferous limestone of Lowick, Northumber- 
land; in the carboniferous shale of Glasgow. 
