CARBONIFEROUS FOSSILS OF IRELAND. 147 



AtHYEIS CONCENTRICA. Voil Buch. SP. 

 Terebratula concentrica. Von Buck. 



S/i. Ch. — Orbicular, convex, an obtusely rounded, mesial fold; surface concentrically striated. 



This species is not uncommon ; it is figured in the Bui. do la Soc. Geol. de France, with a perforated 

 beak, as in Terebratula. I have, however, seen numerous specimens with the beak entire and imperforate, 

 as in the other Paleozoic species. 



Athyris DECUSSATA. SoiV. SP. 

 Atrypa decussata. Sotc. Geol. Trans Spirifera decussata. Phil. Pal. Fos. 



Sp. Ch. — Orblcvilar, length and width nearly equal, convex ; surface marked witli sharp, concentric, im- 

 bricating strlffi, cremdated by very fine, radiating lines. 



This pretty species is very abundant ; it differs from the S. concentrica. Von Buch, in the absence of a 

 mesial fold, and in the distinct, radiating strias. Length eight lines, width nine lines. 



Athyris depressa. M'Cojj. (PL XVIII. fig. 7). 



Sp. Ch. — Transversely oval, depressed; width exceeding the length by one-fifth; surface with equal, 

 transverse, imbricated lamina, having their margins minutely dentato-tubercular ; mesial fold large, undefined, 

 rounded, prominent. 



This fossil occurs in abundance in certain localities ; the specimens are generally more or less crushed, so 

 as in some measure to conceal the characters of the species. The curious, tubercular, tooth-like fringe to the 

 transverse lamlnse will, however, serve to distinguish even fragments of the shell. Length one Inch and a half, 

 width one Inch ten lines. 



Athyris expansa. Phil. sp. 



Spirifera expansa. Phil. Geol. York. 



Sp. Ch. — Transversely elliptical; width very little exceeding the length ; very depressed ; edge obtuse; 

 no mesial fold ; obtuse, imbricating, concentric strlaj, and very faint, radiating lines. 



This species is very nearly allied to the A. glabristria, but wants the mesial fold, which in that species is 

 very prominent ; it Is greatly more depressed, the depth being less than one-third of the width ; the edge Is obtuse 

 in this, but sharp in the former species ; the concentric striae are always present, but never very prominent, 

 as in the Athjris squamosa, they are obtusely rounded, not assuming the form of erect scale-like lamlnse as In 

 that species. The usual length is about one inch three lines ; the width one inch and a half 



Athyris fimbriata. Pliil. sp. 



Spirifera fimbriata. Phil. (Not figured). 



Sp. Ch. — Nearly orbicular; depth half the width; coarse, rounded, radiating striae, decussated irregularly 

 by tUck, prominent, lines of growth ; edge of the valves rounded, obtuse ; no mesial fold. 



I am not aware of any published figure of this species, which is very rare. The radiating strlaa are 

 uncommonly thick, smooth, rounded, but not very prominent ; the concentric ridges are rather irregular in 

 their distance one from the other ; these, together with the blunt edge, give an unshapely appearance to the 

 shell ; it is a small species, rarely exceeding half an inch in length ; the width is very little greater than 

 the length. 



