436 BRITISH PALASOZOIC FOSSILS. [Bracuiopopa. 
ATHYRIS PARADOXA (M°Coy). 
Ref. and Syn. = Actinoconchus paradowus M°Coy Syn. Carb. Foss. Irel. t. 21. f. 6. = Atrypa expansa Sow. Min. 
Con. t. 617. f. 1. lower right-hand figure (not the middle nor left-hand figures) = Terebratula De-Roissyi de 
Vern. Bul. de la Soc. Géol. de France, Vol. XI. t. 3. f. 1 @ and ¢ (not of Eveillé) = Terebratula planosul- 
cata de Kon. Anim. Foss. Belg. t. 21. f. 2. (not Spirifera planosulcata Phill.) 
Desc.—Almost orbicular, sides and front forming three-fourths of one circle; beaks very small, slightly 
projecting, perforation in receiving one small; valves almost equally deep; entering and receiving valves gently 
and evenly convex, without trace of mesial ridge or hollow; lateral and front margins perfectly in one plane, 
without trace of sinus. Surface of both valves occasionally shewing traces of faint, obscure, interrupted, obtuse, 
equal, radiating lines, (eight in two lines at four lines from the beak, four in two lines, at eight lines from 
the beak); also marked with slightly irregular, concentric, imbricating strize, obsolete near the beak, becoming 
gradually stronger towards the margin, where they are prolonged into flat, continuous, nearly semicircular 
plates, often half or three-fourths of an inch in width; when preserved these extended lamellee have a smooth 
space, about half a line wide, where they join the convex part of the valves, the remaining portion being 
marked with flat, radiating sulci; when broken off they merely leave concentric lines of growth, which at the 
adult length of nine lines are greatly thickened. Average width eight lines, proportional length of receiving 
valve “, length of entering valve ,;;, depth of both valves together 55. 
When the extended flattened lamelle are broken off, as is the case in the greater number of specimens, 
they only leave traces of obscure lines of growth (about ten in two lines) so nearly obsolete in all the rostral 
portion that it seems smooth, but shewing by their thickness, and the extreme obtuseness of the edge in 
specimens approaching nine lines in length, that that is the ordinary adult size, although I have seen some 
rather larger, not bearing such marks of age. It is only close to, or immediately at the margin, that we find 
these paradoxical, greatly-extended shelly, flat, radiated lamellze, which if perfect would considerably exceed the 
length of the shell in width. I imagine that they are found at the margins because there the corresponding 
lamellze of the two valves would come in contact and support each other; but, by growth of the shell, they would 
become separated when a new edge was formed between them, leaying them erect, insulated, and liable to be 
broken off by the slightest accident, The same thing can be seen in the recent Tridaena sguamosa, where the 
great scale-like laminee near the beak are always effaced, while those near the margin are perfect ; the rather 
close, flattened, radiating sulcation of those laminze is not divided into spines, as in the A. De-Roissyi; the traces 
of longitudinal radiation occasionally seen on the valves is very partially developed; the spiral appendages are 
very large, the apices of the cones placed at about one-third the length of the front margin. Mr Sowerby 
seems to confound this species with the A. expansa, which however his own figures truthfully shew to be much 
larger, and (by the lines of growth) of a totally different wide, transversely-elliptical figure, at all ages. M. de 
Koninck has confounded it with the Spirifera planosulcata of Phillips, from which it totally differs in figure and 
want of the deep mesial hollow in each valve characteristic of that species. The want of mesial fold in the 
adult, and the lamellz not forming narrow, spinous fringes as well as the regular, obtuse yalves, separate it from 
the A. De-Roissyi, with which M. de Verneuil originally united it. 
Position and Locality —Common in the dark lower carboniferous limestone of Lowick, Northumberland ; 
rare in ditto, Kendal; rare in ditto, Derbyshire. Doubtful specimens in the carboniferous shale of Beith, 
Ayrshire. zy 
ATHYRIS PECTINIFERA (Sow. Sp.) 
Ref. and Syn. = Atrypa pectinifera Sow. Min. Con. t. 616 = Cliothyris id. King, Perm. Foss. t. 10. f. 1 to 10. 
?= Terebratula De-Roissyi M. V. K. t. 9. f. 2 (not of Eveillé) = 7. pectinifera id. id. t. 8. f. 12. 
Desc.—Transversely, very broad-ovate; beaks small, slightly prominent; scarcely any trace of mesial 
ridge or hollow, or sinus in front margin at six lines long, the margins being in one plane; valves almost 
equally deep, sometimes one, and sometimes the other slightly deeper ; greatest depth of each a little behind the 
middle; each valve evenly convex, marked with narrow, imbricating, concentric laminz of growth, which when 
