CARBONIFEROUS FOSSILS OF IRELAND. 169 



SekPULA HEXICARINATA. M'Coy. (PL XXIII. fig. 28). 



Sp. Ch. — Elongate, slightly flexuous, hexagonal; sides nearly equal, smooth, flat; a narrow, rounded, pro- 

 minent keel on each of the angles. 



This species is easily distinguished from any of the other Palaeozoic Serpula, by the hexagonal form of the 

 tube, and the six narrow, rounded keels on the angles. Length usually about two inches, width half a line. 



Serpula parallela. M'Coi/. (PI. XXIII. fig. 30). 



Serpula socialis. Gold. Portk. Gcol. Rep. 



Sp. Ch. — Tubes very slender, cylindrical, smooth, grouped parallel to each other in bundles; tubes one- 

 fourth of a line in diameter. 



Tliis curious species differs from all the Serpnla with which I am acquainted, in being perfectly smooth, 

 and without the irregular flexuosity in any part of the tubes, which we commonly see in the other species of the 

 genus ; the tubes are parallel to each other, forming masses three or four inches long, and one inch in thickness. 

 Wlien preserved in shale they are usually yellowish and semi-transparent, probably owing to their mode of 

 conservation ; in limestone they are white and opaque. It is exceedingly constant In its characters ; as it is 

 certainly not identical with the Serpula socialis, Gold., of the cretaceous period, it seems best to give it a dis- 

 tinctive name. 



Serpula scalabis. M'Coy. (PI. XXIII. fig. 29). 



Sp. Ch. — Cylindrical, very slowly tapering, tortuous ; shell thick ; surface with large imbricating, transverse 

 rings. 



Tliis species is rendered remarkable by the large, regular, transverse rings on the surface of the tube, which 

 is very tortuous. Diameter two lines. 



Spirorbis. Lam. 

 Gen. Ch. — Discoid, spirally coiled, whorls round; attached by the under side. 



Spirorbis caperatus. M'Coy. (PL XXIII. fig. 26). 



Sp. Ch. — Discoid, whorls hardly two, very rapidly enlarging, round, strongly wrinkled concentrically. 

 I have only seen one specimen of this pretty little shell attached to a species of Fenestella; the strongly 

 wrinkled surface will distinguish the species. 



Spirorbis globosus. M'Coy. (PL IV. fig. 10). 



Sp. Ch. — Subglobose, slightly compressed, smooth; volutions concealed by the last whorl ; back broad, 

 rounded ; umbilicus very small. 



This very gibbous species differs from the S. omphalodes, Gold., in the small size of the umbilicus, and 

 the completely concealed volutions; it most nearly resembles the S. valvata of the Muschelkalk. Diameter 

 one line, thickness half a line. 



Spirorbis intermedius. M'Coy. (PL IV. fig. 9)- 



Sp. Ch. — Discoid, flattened ; sinistral ; whorls two and a half, round, nearly equal in thickness throughout ; 

 a few distant, u-regular, ring-like thickenings. 



Tliis species is intermediate between the S. ammonia and the S. omphalodes, having the compressed 

 form, very gradually increasing whorls, and obscurely annulated surface of the former, with a smaller number 

 of whorls, besides which, it differs from both in being sinistral. Diameter one line, thickness one-fourth of a 

 line. 



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