456 BRITISH PALZZOZOIC FOSSILS. [ Bracuiopopa. 
I know of no figure representing the large, subrhomboidal, or fusiform adult. I think I see a trace of 
small dendritic impressions between the adductor impressions, as in Productus, but am not sure. 
Position and Locality—Common in the lower carboniferous limestone near Kendal; the dark, lower, 
limestone of Ronalds-way, Isle of Man; dark carboniferous limestone of Dalton in Furness, Lancashire. 
LeptaNnaA (Chonetes) pouita (M’Coy). PI. 3. D. fig. 30. 
Ref—Ild. M°Coy, Ann. Nat. Hist. 2nd Series, Vol. X. 
Desc.—Transversely fusiform ; hinge-line exceeding the width of the shell, forming narrow, semicylindrical, 
convoluted ears, each bearing four or five small spines. Receiving valve nearly hemispherical, very gibbous in the 
middle and towards the beak, which is large, inflated, and seems considerably to overhang the hinge-line from 
the abrupt contraction of the ears, which are separated by an abrupt curve from the steeply sloped sides; front 
margin slightly elevated in a broad wave, extending its whole width; no mesial furrow. Entering valve almost as 
concave as the receiving one is convex; cardinal area about ten times wider than high; substance of the shell 
thick. External surface of both valves perfectly smooth, or, under a strong lens, with minute concentric striz of 
growth near the margin; internal cast of receiving valve marked with very large quincuncially arranged punc- 
tures, usually about twice their diameter apart; rostral portion divided by a narrow slit left by the mesial 
septum, extending less than half the length of the shell. Width of large specimen four and half lines, propor- 
tional length of receiving valve ;;,, depth =. 
This species has much the form of Leptena (Chonetes) volva (M°Coy), but is not so wide, it is more gibbous, 
and it is the only carboniferous species I know at this date that has a smooth surface. The measurements 
above are from a large Irish specimen in the collection from Mount Rath, the English one being only two lines 
wide. 
Position and Locality.—Rare in the dark carboniferous limestone of Lowick, Northumberland. 
Explanation of Figures.—P1, 3. D. fig. 30. Magnified four diameters, shewing the very coarse scattered 
punctures, and small mesial septum of the internal cast ; and the thick shell, and the smooth external surface 
on the lower right hand portion. The line above indicates the natural size. 
Lerta@NnA (Chonetes) supmintmA (M/°Coy). PI. 3, fig. 31. 
Ref—Ann, Nat. Hist. 2nd Series, Vol. X. 
Desc.—Rotundato-quadrate, length three-fourths or four-fifths of the width. Receiving valve very gibbous 
in the middle, greatest depth a little behind the middle; hinge-line as long as the shell is wide, forming flat- 
tened ears, slightly acute from the sigmoid outline of the sides, having three or four moderately long, slender 
spines on each side of the beak, extending backwards as usual in the plane of the margin; front margin mode- 
rately convex. Surface uniformly covered with close obtuse strize, once or twice branched, but nearly uniform in 
size on all parts of the shell, and so fine, that twelve at the margin only occupy half a line when decorticated ; 
the impressed lines between the strize of the surface very coarsely punctured, and the beak slit by the deep im- 
pression of the mesial septum, extending half the length of the shell. Entering valve nearly as concave as the 
receiving one is convex; surface similar in both valves, the strize being crossed by fine close lines of growth. 
Average width one and half lines, the depth seems about half the width. 
This little species is so extremely like the Silurian Leptwna minima, that it required a comparison of the 
specimens to distinguish them, more especially as the spines of the hinge-line of the present species are not often 
seen; the carboniferous fossil has more uniform and less branched strize, and they are so much finer than in the 
Silurian species, that double the number is uniformly found to occur in the same space of half a line near the 
margin. It is possible that this may prove identical with the Leptena gibberula of my volume on the mountain 
limestone fossils of Ireland, t. 20. f. 11. (which certainly has no relation to my Z. crassistria and sulcata, with 
which M. de Koninck unites it); but as I there described the width as rather greater, and do not give the abso- 
lute dimensions of the fine strize, I hesitate to unite them without a comparison of specimens. 
