148 SYNOPSIS OF THE CHARACTERS OF THE 



Athyris glabristria. Phil. sp. 



Spirifera glabristria. Phil. Geol. York. 



Sp. C/«.— Transversely elliptical, depressed; mesial fold large, prominent, undefined, obtusely rounded; 

 surface smooth or with faint radiating stri». 



This is one of the many smooth Spirifers which runs a risk of being confounded with the Spirifera 

 (Martinia) glabra. That shell has, however, a large cardinal area, while this has no trace of one. The present 

 shell is very constant in general outline, but varies in depth from one-half to one-third of its width ; the beaks 

 are very small ; the sm-face is usually smooth, but, if finely preserved, shows delicate, radiating strite. The lines 

 of growth are only conspicuous near the margin, but do not affect the general smoothness of the surface. 

 Length one inch three lines, breadth one inch ten lines. 



Athyris globularis. Phil. sp. 



Spirifera globularis. Pkil. Geol. York. 



gp ch. Orbicular, ovate, subglobose; mesial fold wide, obtuse; surface smooth, with fine lines of growth. 



This species is rather longer than wide, very gibbous, the depth being equal to about two-thirds the width ; 

 the surface is smooth, with the exception of a few Unes of growth; the mesial fold is wide, but not very promi- 

 nent ; both mesial ridge and furrow are frequently divided by a fine, impressed line. 



The spiral appendages in this species are of great size, filling almost the entire shell ; the apices of the 

 cone, instead of being directed upwards towards the beak, as in the true Spirifers, are directed downwards 

 towards the front margin. This fossil is of very local occurrence in Ireland ; it rarely exceeds three-quarters 

 of an inch in length. 



Athyris hispida. Soiv. sp. 



Atrypa hispida. Sow. Geol. Trans. 



Sp, Ch. — Transversely oval, convex; beaks small ; surface concentrically imbricated by broad lamellae ; 

 concentrically fringed, with strong, spine-like striaj. 



When well preserved the Athyris decussata puts on precisely the surface of this species, the concentric 

 striae of that shell being the basis, or remains of concentric, broad lamellae, such as we see in the Actinoconchus 

 paradoxus and Athyris squamosus, and being, in both shells, decussated by similar strong striai, which give a 

 fringed appearance to the surface when irregularly worn. Length six lines, width seven lines. 



Athyris planosulcata. Phil. sp. 



Spirifera planosulcata. Phil. Geol. York. 



Sp, CA.— Pentahedral, depressed at the sides, tumid in the middle ; centre of each valve with a broad, well- 

 defined mesial sulcus. 



The surface of this curious species is perfectly smooth, it is very much depressed at the sides, but some- 

 what tumid in the middle, the ventral valve having a mesial hollow, as well as the dorsal, forms a very peculiar 

 character. About an inch in length, width very little greater than the length. 



Athyris squamosa. Phil. sp. 



Spirifera squamosa. Phil. Geol. York Spirifer lamcllosiis. Leveille, Mem. Geol. Soc. de France — Spirifer De Eoissyi. 



Lev. Mem. Geol. Soc. de France. 



Sp, Ch. Transversely elhptical, or subrhomboidal ; depth half the width; mesial fold narrow, prominent; 



frequently divided by a mesial sulcus ; surface with distant, erect, concentric laminjE of growth. 



