CARBONIFEROUS FOSSILS OF IRELAND. 123 



In form this resembles the O. crenistria, but is easily distinguished by its very numerous, flexuous, rounded 

 stria;, which, instead of being unequal in length and thickness, and separated by broad, flat, spaces, as in that 

 species, are in the present shell equal, and ])ei'fcctly close together, resembling coarse, flowing hair ; the obtuse, 

 flexuous, and very numerous strife distinguish it from the 0. Bechei, M'Coy (see O. Bechei). Length one inch 

 six lines, width two inches seven lines. 



OrTHIS COMPRESS A. SoW. (?) 



Orthis compressa. Sow. (?) Sil. Syst Orthis compressa. Phil. Pal. Fos. 



Sp. Ch. — Truncato-orbicular, depressed; length and width nearly equal; surface with very fine, radiating 

 striffi, having between them rows of impressed puncta. 



A few imperfect specimens, apparently of this species, have occurred. 



Orthis connivens. Phil. sp. 



Spirifera connivens. Phil. Geol. York. 

 Sp. Ch. — Globose; front margin much raised and sinuated; a mesial hollow, bounded by two obtuse 

 ridges, in each valve ; surface with coarse, radiating strise. 



Orthis crenistria. Pliil. 



'Spirifera crenistria. Phil. Geol. York — Orthis crenistria. Sow. Geol. Trans. — Orthis crenistria. Phil. Pal. Fos. 



iSjo. Ch. — Semicircular; cardinal area large, strongly striated; foramen nearly closed by vaulted scales; 

 greatest depth of convex valve about one-third from the beak ; radiating strias strong, sharp, unequal in thick- 

 ness, increasing in number towards the margin ; spaces between the radiating stria flat, sharply striated across. 



In old individuals the front becomes as much deflected as in the LeptcBiia eughjpha. 



Orthis CYLiNDRic A. M'Coy. (PI. XXII. fig. I). 



Sp. Ch. — Ventral valve semicircular, evenly convex, very gibbous towards the beak; deflected front very 

 long, convex, cyhndrical ; surface marked with fine, longitudinal ridges, every fourth or fifth larger than the 

 others ; the intervening spaces slightly wrinkled transversely, with very fine longitudinal stria. 



The striation of this beautiful shell is similar in character to that of the O. crenistria, O. Kellii, L. euahi- 

 pha, &c., but the form at once distinguishes it from every other known species ; it approaches somewhat to the 

 L. euyhjpha, but is much longer, more cyhndrical, and convex ; even young shells may be distinguished by all 

 the space near the beaks being flattened, or slightly concave in the one, but very gibbous in the other. Length 

 of rostral portion eight lines ; length of the deflected front one inch two lines ; width one inch two lines. 



Orthis divaricata. M'Coy. (PI. XX. fig. 17). 



Sp. Ch. — Transversely oval; ventral valve evenly convex ; dorsal valve plano-concave in the middle; 

 hinge-line very short; surface finely and regularly striated; stnx at the sides much curved. 



This species is mucli larger, and more convex than the O. arcuata, Pliil., which, in some respects, it much 

 resembles ; it is likewise more finely striated, and much less transverse, the width exceeding the length by 

 rather less than one-fifth, while the O. arcuata is nearly twice as wide as long; it has, also, a larger cardinal 

 area. Length twelve lines, width fomteen lines. 



Orthis filiaria. Phil sp. 



Spirifera filiaria. Phil. Geol. York. 

 Sp. Ch. — Longitudinally obovate, depressed; beaks prominent; hinge-margin very short, widest towards 

 the front ; smaller valves concave in the middle ; a shallow sinus in the front margin ; surface coarsely striated 

 longitudinally. 



