Bracutiopopa. | UPPER PALAZOZOIC MOLLUSCA. 413 
strongly marked, and extending nearly from the beak to within one-third of the length of the front margin ; 
dental lamellz strong; entering valve evenly convex in the middle, gradually arching to the margins, usually 
without trace of mesial ridge or hollow ; but in old specimens of six lines long a very shallow obsolete indentation 
may be noticed at the edge; surface smooth, closely punctured under the lens, or with a few interrupting lines 
of growth near the edge of large specimens. Average length six lines, proportional length of entering valve =, 
width =, depth of entering valve ;, depth of receiving valve =. 
The greater gibbosity, more obtuse margins, small, definite lobe in the front margin, and the corresponding 
long, narrow mesial sulcus of the receiving valve, easily distinguish this species from the most, nearly allied 
varieties of the S. elongata ; the sides of the beak are also more obtusely rounded or less angulated. The distinct 
upward arching of the middle of the front margin, as well as the absence of mesial furrow on the entering valve, 
distinguish it from the S. saceulus of the carboniferous rocks, to which the receiving valve approximates very 
closely. I have found the adult specimens of this species distinguished in Count Munster’s collection from 
Gliicksbrunn, under the manuscript name 7’. swbsinuosa. 
The want of spirals, and the punctured, instead of the fibrous tissue, separate this species easily from 
certain narrow varieties of the carboniferous Athyris sublobata (Port. Sp.) or A. ambigua (Sow.), to which, 
in outward form, it strongly approximates. 
Position and Locality — Common in the Permian limestone of Humbleton Hill. 
SEMINULA VIRGOIDES (A/*Coy). PI. 3. D. fig. 23. 
Ref. and Syn.=Atrypa virgoides M°Coy, Synop. Carb. Foss. Irel. t. 22. f. 21. ?= Terebratula fusiformis 
M. V. K. Geol. Russ. t. 9. f. 8. ?= 7. hastiformis de Kon. Anim. Foss. Bel. Suppl. t. 56. f. 8. 
Dese.—Longitudinally oblong, or very obscurely ovato-pentagonal, gibbous ; front narrowed to nearly half 
the greatest width; anterior lateral margins considerably longer than the front, greatest width a little in front of 
the middle in most specimens. Receiving valve moderately gibbous, most so at one-third from the beak, from 
whence the profile arches gradually to the front margin, and more rapidly to the beak, which is large, prominent, 
and moderately incurved, having a very obtuse angulation on each side, and at its apex a large oval foramen ; 
moderately convex in all the middle portion, sloping with a less convexity to the margins, which are moderately 
obtuse, and with a broad, regular curve towards the receiving valve from the beak to the front; after about four 
to nine lines from the beak, a shallow, wide, mesial concavity is gradually developed in most specimens, extending 
to the margin, which it raises with a gradual undefined curve of its whole width towards the entering valve 
(those specimens in which the mesial hollow is not developed have the front margin straight); entering valve 
very tumid along the middle, arching gradually from the beak to the front margin, which is not affected by the 
wave in the margin, shewing no trace of mesial ridge or sinus; greatest depth about the middle, sloping rapidly 
with slight convexity to the side margins, (when decorticated exhibiting commonly three or five very strong, 
angular, longitudinal ridges, radiating from the beak) ; surface nearly smooth, or marked with coarse imbricating 
irregular concentric lines of growth, strongly reticulo-punctate under the lens. Length of very large specimen 
one inch six lines, proportional length of entering valve **, width 4%, depth of entering valve =, greatest depth 
of receiving valve 2; length of small specimen eight lines, proportional length of entering valve 5, width 7, 
depth of both valves =. 
Some small specimens, with the largely-marked mesial hollow, approximate so nearly to the Permian 
S. sufflata, that Professor King, in his book on the magnesian limestone fossils (for I suppose this is the species 
he alludes to at page 150, as the mountain limestone-shell from Bolland), seems to consider them identical ; it is, 
however, distinct by its less tumid sides, by wanting the narrow, defined mesial sulcus of the receiving valve, and 
the corresponding distinctly marked upward indentation of the front margin; the punctation of the surface is also 
much coarser in the present species than in the magnesian limestone one. It is, perhaps, most closely allied to 
some specimens of the magnesian limestone, S. elongata ; but the mesial hollow of the receiving valve, instead of 
being as wide as the entire front, rendering the greater part of the anterior portion of the valve concave, 
is either entirely absent, or comparatively narrow, confined to the middle portion of the shell defined by the 
