192 BRITISH PALALOZOIC FOSSILS. [Bracuiopopa. 
2. Sub-genus Bracuytuyris (MMCoy).—General characters of Spirifera, but the hinge-line shorter than 
the width of the shell, and the cardinal angles obtusely rounded. 
8. Sub-genus Marrinia (JM*Coy).—General characters of Brachythyris, but the surface smooth, without 
radiating ribs; spiral appendages very small. 
SPIRIFERA BIFORATA (Schlot. Sp.) 
Ref. and Syn. =Terebratulites biforatus Schlot. Petrefacten, p. 265. 
This species has been made the type of a new genus of Orthisidw, by Professor King, but both he and 
M. de Verneuil in forming for it his group, “ bifores,” of Spirifer, seem to have overlooked the double area 
and foramen pointed out in the true carboniferous Spirifers by d’Orbigny, and which certainly exist. 
There are several varieties of this species which I describe separately. 
Var. a. SPIRIFERA LYNX (Kichiv. Sp.) 
Ref—M. V. K. Geol. Russ. t. 3. f.3 and 4, Hall. Pal. N. Y. t. 32. D. 
Sp. Ch.—Subquadrate, lateral margins subparallel; apical angle about 145°; valves very gibbous, entering 
valve most so; hinge-line as wide as the shell; cardinal area rather narrow, of nearly equal width in both 
valves, and each area with a nearly equal triangular opening; mesial ridge quadrate, very prominent, sharply 
defined to the beak, forming a deep oblong sinus in the front margin, mesial ridge with four simple, obtusely 
angular plaits, sides with from five to eleven simple, angular plaits, about the same size as those on the 
sinus; substance of shell thick, fibrous, the ends of the fibres giving a slightly granulose aspect to the surface 
in some conditions, under a high power: cas¢s of receiving valve shew the usual small ovate rostral prominence 
bordered by the short strong dental lamellee, and the shoulder-like lateral lobes usual in the genus; the enter- 
ing valve shews a small ovate prominence of the beak, with a deep oval diverging pit on each side for the 
apophyses ; from these on each side extends a rotundato-quadrate, sulcus enclosing a space as long as wide, the 
width about a third greater than that of the mesial ridge, this space divided by a crucial sulcus into four 
subequal rotundato-trigonal muscular impressions. Average width one inch two lines, proportional length of 
receiving valve =4, of entering valve ;7;, depth 75. 
Position and Locality Extremely common in the Upper Bala sandstone of Alt yr Anker, Meifod, Mont- 
gomeryshire ; schists of Pen y Craig, Llangynyw, Montgomeryshire; schists upon Bala limestone at Bryn Melyn 
quarry near Bala, Merionethshire ; schists of High Haume, Dalton in Furness, Lancashire ; schists of Bwlch 
y Ciban; schists upon Bala limestone of Maes Meillion, S. of Bala, Merionethshire; Pont y Glyn, Diffwys, 
W. of Corwen, Merionethshire ; concretionary limestone of Maes y fallen, Bala (small specimen with trace of 
branching on some of the lateral ribs indicating a passage to the Var. S. terebratuliformis, M°Coy). 
Var. 8. SPIRIFERA DENTATA (Pand. Sp.) 
Ref. and Syn. = Porambonites dentatus Pander Beitr. z. Geol. Russ. t. 11. f. 4. Spirifer id. 
M.V.K. Geol. Russ. t. 3. f. 5. 
Sp. Ch.—General characters of the S. Zyna, but the width rarely reaching nine lines, the simple lateral 
plaits six to eight in number, mesial plaits constantly two in the sinus and three on the meisal ridge; sub- 
stance of the shell coarsely punctured. 
Position and Locality—Not common in the Bala schists of Coniston Water Head, Lancashire ; schists 
of Cyrn y Brain, Wrexham, Denbighshire ; and schists of Rhiwargor, near Llanwddyn, Montgomeryshire. 
Var. y. SPIRIFERA BIFORATA (Schlot. Sp.) (Vera.) 
Ref.—M. V. K. Geol. Russ. p. 135. 
Sp. Ch.—General characters of the preceding varieties, but the shell usually wider in proportion to the 
length, the ribs narrower and more numerous, mesial fold wider and less elevated, bearing usually from six to 
