CARBONIFEROUS FOSSILS OF IRELAND. 143 



Reticularia imbricata. Sow. sp. 



Terebratula imbricata. Sow. Min. Con Spirifera imbricata. P/ul. Gcol. York . 



Sj>. Ch. — Transversely oval; strong, obtuse, radiating striiE, interrupted by broad, thick, imbricating 

 lamellae ; no mesial fold. 



This is distinguished from the M. Uiieata by its thick, radiating strias, and the distance between and 

 small number of the transverse strije, which, in the present shell, form between them about ten or eleven thick, 

 imbricated, concentric laminae, each about a line in breadth. Length one inch, width one inch four lines ; 

 usually found in company with the Reticularia lineata. 



RETICtTLARIA LINEATA. Mart. SP. 



Anomites lineatus. Martin, Pet. Derb Terebratula lineata. Sow. Min. Con. — Spirifera lineata. Phil. Geol. York. 



Sp. CA.— Transversely oval, convex; no mesial fold; surface with close, imbricated, transverse lines. 

 This very elegant species abounds in the limestone of Little Island, Cork, but is not very common any 

 where else. It has been figured and described by Sowerby as a Terebratula, not having found the spiral 

 appendages in it. The beaks and cardinal area are very small ; the concentric lines are very numerous and 

 regular ; the two cardinal teeth of the ventral valve are thin, narrow, their bases slightly converging towards 

 Fig. 26. the beak ; those of the dorsal valve are broader and thicker ; the cicatrices of the upper pair 



of muscles in the ventral valve form two small, deep, oval cavities (elevations in the cast) ; 

 their long diameters parallel to each other, and directed towards the beak, from which 

 they are about their own length distant ; the cicatrices of the similar pair of muscles, in the 

 dorsal valve, are confluent, forming one round, undivided cavity, distant twice its lengtli 

 from the hinge-line (see fig. 26; A A, origin of upper pair of muscles in ventral valve; b, 

 origin of upper pair in dorsal valve). Length nine lines, width one inch. 



Reticularia microgemma. Phil. sp. 



Spirifera microgemma. Phil. Pal. Fos. 



Sp. Ch. — Orbicular, gibbous ; mesial fold rounded, prominent; beak of the dorsal valve large, tumid; very 

 fine, radiating striae, and numerous imbricating lamina of growth, the edges of which, when crossed by the ra- 

 diating striae, are ornamented with minute, rounded tubercles. 



This is known from the Reticularia imbricata by the prominent mesial fold; the greater number of the 

 transverse lamella', the delicacy of tlie radiating stria;, and the little tubercles at the intersection of the lines ; 

 from Reticularia reticulata it is distinguished by its prominent, undefined, mesial elevation, its flattened la- 

 minse of growth, and its tubercles. Length eight lines, width ten lines. 



Reticularia reticulata. M^Coy. (PI. XIX. fig. 15). 



Sp. Ch. — Transversely oval; about thirty round, undulating, concentric wrinkles, decussated by exceed- 

 ingly fine, close, radiating striae; a faint, but defined mesial fold. 



This beautiful little species is at once distinguished from the R. imbricata, Phil., by all its markings being 

 infinitely smaller, and more delicate; the transverse lamina;, instead of being broad and flat as in that species, 

 are very narrow, rounded, and fle.xuous, and are fully three times the number in the present shell; the 

 radiating strise are in proportion finer and more numerous. The mesial elevation, though nearly as flat as the 

 rest of the shell, is defined on each side by a sharp, impressed line ; tlie mesial hollow is deep and also defined 

 by two obtuse ridges extending to the beak. Length eight lines, width eleven lines. 



