Bracutoropa. | UPPER PAL/ZOZOIC MOLLUSCA. 433 
Atuyris Dr-Rorssyi (L’Eveillé Sp.) 
Ref. and Syn. = Spirifer, id. id. Mém. de la Soc. Géol. de France (1835) Vol. II. t. 2. f. 18 to 20.= Terebratula 
id. de Kon. Anim. Fos. Bel. t. 20. f. 1 and t. 21. f.1 (excl.e. f. i.) ;4 = Athyris depressa M°Coy, Syn. Carb. 
Foss. Irel. t. 18. f..7;?=Spirifera fimbriata Phill. Geol. York. Vol. II. p. 220. 
Desc.—Transversely oval, depressed, or moderately gibbous ; lateral and front margins nearly in one plane, 
till after half an inch in length, when in some specimens a semielliptical sinus becomes developed in the front 
margin, with a corresponding concave mesial hollow in the receiving valve, and a smaller, undefined, rounded, 
mesial ridge in the entering valve, both becoming stronger with age, but in some specimens not making their 
appearance at one inch from the beak; entering valve gently convex ; greatest depth about one-third from the 
beak, which is tumid and prominent. Receiving valve moderately convex; greatest depth at about the middle 
of the length; beak narrow, small, tumid, incurved, with a moderate opening at the apex. Surface of both valves 
(in limestone specimens) almost smooth, or with very fine, concentric, imbricating strize, every fifth or sixth of 
which (at about half a line apart) are more prominent than the rest : when finely preserved the concentric laminze 
form broad fringes of equal, obtuse, narrow, flattened spines, united at their bases, to the concentric lamin, 
which are separated, after about one-third of a line, by spaces varying from one-fourth to rather more than the 
width of the spines, lying close to the surface (about eight in two lines, at six lines from the beak, twelve in 
same space at two lines from the beak), giving either a spinulose, tubercular, or longitudinally suleated, appear- 
ance to the surface, according to the perfection of the preservation; the radiatingly-lined appearance of some of 
the specimens being produced by the spines of the several concentrie rows overlapping each other often in regular 
lines. Width of average specimen one inch three lines, proportional length of receiving valve =, of entering 
valve 4, depth of both valves about {;, but often much less, width of sinus when strongly marked =, depth 
thereof 3, length of spines occasionally one line. 
This species varies extremely in the appearance of the surface according to the mode of preservation ; 
some rare specimens, like the original one figured by I’ Eyeillé, seeming smooth even under a moderate lens, with 
a few distant imbricating lines of growth; and these are so unlike the forms well preserved in shales, that I 
formerly supposed them different. The equal, thick, longitudinal spines, which fringe the narrow, concentric 
lamellze of shale specimens, form an extremely marked character, and by their great strength and coarseness 
separate the species certainly from the Devonian A. concentrica, V. Buch. Sp. 
I have sometimes seen this confounded with the Spirifera (Martinia) lineata, and imbricata, from which 
the complete want of cardinal area between the beaks distinguishes it. It is very probable that the Spirifera 
jimbriata of Phillips is founded on the depressed shale specimens of this species from the shales of Florence 
Court. 
Position and Locality—V ery common in the carboniferous shales of the Isle of Man. 
ATHYRIS EXPANSA (Phill. Sp.) 
Ref. and Syn.= Spirifera id. Phil. Geol. York. Vol. IT. t. 10. f. 18 = Atrypa id. Sow. Min. Con. t. 617. f. 1. 
(only the larger figures) and A. fimbriata (not of Phill.) same plate, f. 4. 
Desc—Transversely elliptical, greatly depressed, nearly equivalve; beaks very small, adpressed; sides 
narrow, semielliptically rounded; front very widely arched, most prominent in the middle; no sinus in the 
margins, which are in one plane; edges obtuse, greatly thickened ; entering valve slightly and evenly convex, 
without mesial ridge or hollow, greatest depth about the middle ; receiving valve slightly and evenly convex 
near the beak, which is very small and adpressed ; surface of the valves becoming gradually flattened towards. 
the margins ; greatest depth at about one-third from the beak ; surface of both valves with fine, subequal, con- 
centric, imbricating strize, about eight or nine in two lines on all parts of the shell, crossed by equal, very obtuse, 
radiating, thread-like strize, most distinct near the beaks, about twelve in the space of two lines, some of which 
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