132 SYNOPSIS OF THE CHARACTERS OF THE 



diminisli rapidly in size from the mesial fold, and are almost perfectly round. Length four lines, width one 

 inch three lines, depth four lines. 



This little species might be regarded as the type of a subgenus, {Fusella, M'Coy) which might be thus 

 characterized. 



Gen. Ch. — Shell elongate transversely, fusiform; cardinal area -wide, much curved; beaks incurved. 



This group would embrace these little Spir/fers of the mountain limestone, which liave a perfectly fusiform 

 outline, the depth being equal to the length, and the sides cylindrical ; the cardinal area is extremely wide in 

 proportion to their size, and is always hollowed, or much curved, thus contrasting -with the narrow, flat area of 

 the typical SpLrifers, while the strongly incurved beaks distinguish them from the Cyrtia. It would include 

 the S. hicarinata, S. rhomboides, &c. &c. 



Spikefera gigantea Sou: 



Spirifer giganteus. Soic. Geol. Trans Spirifera gigantea. P//iL Pal. Fos. 



Sjj. Ch. — Transversely elongate; sides cuspidate, mesial fold defined; about twenty -five narrow entire 

 ribs on each side, crossed by numerous lines of growth. 



This large species is not uncommon in some localities in L'eland ; it has been confounded by some of the 

 English geologists with the S.princeps, from which it differs in its slender and more numerous radiating ridges. 



SpIRITEEA GKANDiEVA. P/lil. 



Spirifera grandaeva. Phil. Pal. Fos. 



Sp. Ch. — Truncato-orbicular, front narrow, sides nearly straight, gibbous; cardinal angles acute, mesial 

 fold broad, rounded, well defined ; about nine or ten large, rounded ribs on each side the mesial fold, on which 

 there are about five ridges equal in size to those of the sides. 



A single specimen of this very rare species has occurred; it is distinguished from the S. aperturata by the 

 greater size of the ribs on the mesial fold. 



Spirefeea inoenata. Sow. 



Spirifer inornatus. Sow. Geol. Trans. 



Sp. Ch. — Nearly four times as wide as long, convex ; surface irregular, smooth, with a few unequal, trans- 

 verse waves of growth. 



A few imperfect fragments of tliis species have been found. 



Spieifera megaloba. Phil. 



Spirifera megaloba. Phil. Pal. Fos. 

 Two or three large, rounded, transversely imbricated ribs belonging to this species have occurred. 



Spieifeea mesomala. Phil. 



Spirifera mesomala. Phil. Pal. Fos. 

 Sp. C^.— Semicircular, depressed; mesial fold broad, flat, smootli, and sharply defined, about ten narrow, 

 rounded, equal ribs on each side. 



Spirieeea minima. Sow. 



Anomites acutus. Mart. Pet. Derb. — Spirifer acutus. Flem. — Spirifer minimus. Sok. Min. Con. 



Sp. C/i.— Semicircular, convex, length two-thirds the width ; ribs deep, equal; mesial ridge and furrow 

 angular ; cardinal area small ; cardinal angles obtuse ; beak of dorsal valve prominent, incurved. 



