Bracuroropa. | UPPER PAL/EOZOIC MOLLUSCA. 437 
well preserved are at a slight distance from the base, divided into fringe-like rows of slender spines, lying flat on 
the surface, arranged in almost continuous radiating lines, and leaving a faint obtuse lineation on the shell in 
their absence (about ten of these strie in the space of two lines at four lines from the beak) ; beak of receiving 
valve moderately incurved, with a small round perforation at the apex, sometimes appearing open to the hinge. 
Width about seven lines, proportional length of receiving valve 7%, of entering valve 2, depth of both valves * 
to =. 
Te the large, wide, depressed, Permian shell, with the strong mesial sinus in the margin beyond six lines 
long, figured in the Geology of Russia under the name 7’. De-Roissyi, belongs to the present fossil, it would be 
exceedingly difficult to separate the Permian and carboniferous species, the only apparent difference being the 
rather finer radiating fimbriation. None of the English specimens, however, of A. pectinifera have been observed 
of the size at which the mesial ridge and furrow of A. De-Roissyi begin to be developed; this character alluded 
to by M. de Verneuil and Professor King as distinctive therefore fails. The only difference which strikes me 
between the species being a slightly greater coarseness of fimbriation in the carboniferous one; but all Sowerby’s 
and King’s figures represent this radiation as too coarse when compared with the specimens I have examined 
from Humbleton. Professor King does not seem to have found the mesial septum of the entering valve ; 
I have seen it however distinctly marked. 
Position and Locality.—Not uncommon in the Permian magnesian limestone of Humbleton. 
ATHYRIS SQUAMIGERA (de Kon. Sp.) 
Ref. and Syn. = Terebratula id. id. De Koninck, Sup. Anim. Foss. Bel. t. 56. f. 9. 
Desc.—Rotundato-rhombic, or transyersely very broad-oval, tumid; lateral margins slightly sigmoidal, 
front very abruptly raised into a semielliptical sinus at an angle of about 100°, therefore slightly indenting the 
middle of the front margin of the entering valve. Entering valve very gibbous in the middle, greatest depth a 
little behind the middle, gradually arching to the margins; beak obtuse, prominent; after a length of five lines 
a narrow, rounded, or rotundato-quadrate mesial ridge, extends to the abrupt sinus in the front margin ; 
receiving valve gibbous, gradually arched towards the lateral margins, with a deep, concave, mesial hollow, 
commencing at or within a line of the apex of the beak, becoming more strongly defined by two obtuse ridges 
near the front margin; beak large, tumid, much incurved; foramen large. Surface of both valves covered with 
regular radiating, obtuse, equal, flattened strize (averaging twelve or fourteen in two lines over the surface), 
crossed under the lens by faint, rather closer, subregular, concentric strize, a few of which towards the margin 
after half an inch in length become strong, imbricating, interruptions of growth. Average width ten lines, 
proportional length of receiving valve jj, length of entering valve 4, depth of entering valve *,, of receiving 
valve about =, width of sinus in front margin 4, depth thereof *. 
The specimens which I have examined are rather more tumid at the sides, and slightly less wide than 
Professor de Koninck’s figures; but there can be no doubt of their identity. The species has a general 
resemblance to the A. concentrica and A. De-Roissyi in form, but is rather more obtuse, and has the mesial 
hollow in the receiving valve stronger, and nearer to the apex of the beak, than in those species, from which 
it is completely distinguished by the beautifully regular, obtuse, longitudinal striation, and the less marked 
concentric sculpturing. 
Position and Locality.—Not very uncommon in the carboniferous limestone of Derbyshire. 
Genus. SPIRIGERINA. See page 197. 
SPIRIGERINA? Mantra (Sow. Sp.) 
Ref. and Syn. = Terebratula id. Sow. Min. Con. t. 277. f. 1. 
Dese.—Longitudinally ovate, valves almost equally deep ; commissure of the valves deeply reflexo-dentate 
by the extremities of about thirteen or fourteen very strong, prominent, subequal, angular ridges, separated by 
