CARBONIFEROUS FOSSILS OF IRELAND. 85 



AvicuLA Thompsoni. Forth, sp. 



Pterinea Thompsoni. Portk. Geol. Rep. 



Sp. Ch. — Transversely elongate, diagonally gibbous; beaks small; anterior wing pointed, separated from 

 the body of tlic shell by a small sinus in the front margin, opposite the beak, from whence a furrow extends to 

 the beak ; posterior wing falcate, terminating in a long slender spine ; surface with concentric, imbricating 

 lines of growth. 



This is a very distinct and beautiful sjjecies, the long, spiniform extremity of the posterior wing is a curious 

 peculiarity. Length of hinge-line ten lines, from the beak to the posterior extremity five lines. 



AvicuLA Veeneuilii. il/'Coj/. (PI. XIII. fig. 19). 



Sp. Ch. — Transversely subtrigonal; beaks very narrow, small, terminal; posterior side broad, flattened, 

 forming an obtuse angle at the hinge-line, which Is less than two-thirds the length of the shell, and obtusely 

 rounded at the posterior end ; au obtuse, slightly sigmoldal keel extends from the beak to the posterior extremity ; 

 surface marked with fine, irregular lines of growth. 



This shell Is allied to the Avicula Goldfussi, De Ver., and to the A. Saturni, Gold., but Is distinguished 

 from both by its more slender form, shorter hinge-line, and by the posterior end being oval or rounded, Instead 

 of being subtruncate, as In those species ; the ridge from the beak to the posterior end is also straighter and 

 more obtuse In the present shell. Length from the beak to the posterior end two Inches two lines, from the 

 posterior cardinal angle to the oj^poslte abdominal margin one inch. 



Pinna. Linn. 

 Gen. Ch. — Equlvalve, triangular; umbones terminal; extremity widely gaping ; hinge-margin straight, 

 teeth none ; anterior margin slightly gaping. 



Pinna flabellieormis. Mart. sp. 



Conch. Pinnites flabelliformis. Mart. Pet. Derb. {C.P. nudus in the Syst. Arrangement).— Pinna costata. P/iil. 



Geol. York. 



Sp. Ch. — Lanceolate, trigonal, narrow, convex; beak and sides of the shell smooth; surface with regular, 

 narrow, straight ribs, separated by concave, smooth spaces. 



This elegant species occurs but sparingly ; the nearly parallel, regular, mesial ribs, and the wide, smooth, 

 intervening spaces, easily distinguish It from the others. As only fragments have come before me, I cannot 

 give the correct measurements. Professor Phillips' figure represents the beaked portion, which is deficient in 

 Martin's figure, in which latter there Is no smooth part shewn. 



Pinna flexicostata. A-P Coy. (PL XIX. fig. 1 ). 



Sp. C/t.— Elongate, triangular, very gibbous; ventral margin smooth or marked with few obhque wrin- 

 kles ; rest of the surface marked with narrow, equal, flexuous sulci, having between them smooth, rounded, 

 slightly flexuous ridges of unequal width. 



From the P.flahelUformis, ]\Iart., this species Is distinguished by having the ventral third of the surface 

 destitute of radiating ribs, aud in the longitudinal ridges being Irregularly unequal In width, and In their being 

 flexuous; it difl'ers from the P. inaquicostata. Port., in having the two sides similarly marked; from all three 

 It difiers In the longitudinal ridges being flexuous. Length about four Inches, width about one and a halt 

 Inches. 



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