414 BRITISH PALAZOZOIC FOSSILS. [Bracuiopopa. 
tumid lateral portions, and not extending so near the beak: the margins of the Permian species are charac- 
teristically acute, from the much less angle at which the valves meet at the margin; in that species also the 
beak is much more incurved, and more strongly angulated on the sides. The want of the flattened mesial 
hollow on the anterior part of the entering valve easily separates the species from the S. hastata. The figure7of 
T. elongata, given by Romer in his Versteinerungen des Hatzgebirge, t. 5, f. 20, seems rather to represent this 
species. 7. virgo, is distinguished by its radiating striz and unangulated beak. 
Position and Locality—Common in the dark carboniferous limestone, Isle of Man; rare in the dark lower 
limestone of Lowick, Northumberland ; and in the similar limestone of Kendal, Westmoreland. 
Explanation of Figures —PI|. 3. D. fig. 23, from the limestone of the Isle of Man, end view, natural 
size, (most specimens shew a greater upward curve in the front margin); fig. 23a, do. same specimen side view; 
fig. 234, do. receiving valve; fig. 23c, do. shewing traces of the internal ridges of the interior of the valve, 
with a portion of shell near the front edge; fig. 23d, do. surface magnified to shew the reticular marking 
between the punctures. 
5th Family. SPIRIFERID. See page 191. 
Genus. SPIRIFERA. See page 191. 
SPIRIFERA ALATA (Schlot. Sp.) 
Ref. and Syn. = Terebratulites alatus Schlot. Leonhard’s Taschenb. Vol. VII. t. 2. f. 9. + Spirifer undulatus 
Sow. Min. Con. t. 562. f. 1. =(Trigonotreta alata + T. undulata King, Perm. Foss. t. 9. f. 1 to 17.) 
Desc.—Transversely fusiform or rhomboidal ; hinge-line exceeding the width of the shell; cardinal angles 
acute, but the sides of the shell varying greatly in attenuation; cardinal area wide, with nearly parallel sides ; 
receiving valve gibbous; beak large, prominent, much incurved, greatest depth at one-third from the apex ; 
triangular foramen nearly closed, except at the base in the adult, by a strongly imbricated, convex, pseudo- 
deltidium, sometimes visible externally ; mesial hollow wide, strongly defined, concave, smooth, or with obsolete 
traces of one or three longitudinal ribs; each side with twelve or fourteen (only six in some small examples) 
strong, rounded, cord-like ribs, which have commonly been produced from little more than half their number 
near the beak, each primary one of which bifureated once at a very variable distance between the beak and 
margin ; entire surface crossed by subregular, imbricating, concentric, scale-like laminze of growth (averaging 
seven in two lines), which seem undulated by passing over the ridges ; crossed under the lens by rather coarse 
longitudinal fibres of shell-tissue. Entering valve varying greatly in convexity; beak prominent, incurved, with 
a rather large cardinal area nearly in the plane of the lateral margins; mesial elevation obtusely angular or 
rounded ; ribbing of the sides and transverse lamination as in the other valve. Average width two inches, 
proportional length of receiving valve varying from “, to %, length of entering valve % to 4, depth of receiving 
valve =, depth of entering valve }* to 4, width of cardinal area of receiving valve 4, of entering valve 5. 
Professor King is of opinion that this should be considered a punctated shell ; but with a power of half an 
inch focus the tissue seems very distinctly and densely fibrous, and I do not think the excessively minute 
roughening produced by the ends of the fibresshould be confounded with a true punctured tissue. He also thinks 
that the rather more longitudinal rhomboidal forms figured by Sowerby, and those with still shorter hinge-lines 
should be considered a distinct species under Sowerby’s name, S. undulatus, from the very wide, attenuated 
fusiform varieties, to which he would restrict Schlotheim’s name, alatus, the former of which he thinks is not 
found in Germany, and to be distinguished from Schlotheim’s form by a less transverse elongation, and greater 
tumidity at the beaks. It is curious, however, that all the continental specimens in the Miinsterian collection 
at Cambridge, under Schlotheim’s name, alatus, are of the variety which Professor King would call S. wndu- 
latus of Sowerby ; and, on the other hand, all the original specimens of the English fossil, collected by Professor 
Sedgwick, and numbered by Sowerby, belong to the proposed distinct species, S. alatus. The proposed 
distinction of the tumidity of the beaks will not hold either, as the two greatest extremes which I have observed 
