CARBONIFEROUS FOSSILS OF IRELAND. 75 



rounded ; beaks very small, not prominent ; posterior end rounded ; the transverse striae are scarcely visible on the 

 sandstone casts which I have seen, but seem to have been distant, and strongest on the posterior slope. 



MoDioLA Macadami. Portk. 



Modiola Macadami. Portk. Geol. Eep. 



Transversely ovate, gibbous ; shell thin, inflated, marked with rather distant, irregular, deep, concentric 

 striaj ; liinge-margin angulated. 



This is a very variable shell, length six Hues, width one incli two lines. 



Modiola megaloba. M'Coy. (PL XL fig. 31). 



Sj). Ch. — Transversely ovate, gibbous; beaks small, subterminal; anterior lobe exceeding half the length 

 of the shell, defined by a strong sulcus from the beak ; hinge-line two-thirds the length of the shell, angulated. 



This is one of the very few instances in wliich the true, anteriorly lobcd, recent, and OoUtic form o£ Modiola 

 has been found in the older rocks. It differs from the 31. antiqua, Gold., in being very much narrower 

 towards the beaks, and in its angulated hinge-margin. From the beak to the posterior extremity five lines ; 

 from the cardinal angle to the opposite ventral sinus three Unes. 



Modiola patula. M'-Coy. (PI. XIIL fig. 13). 



Sp. Ch. — Lengthened, spatulate, gibbous, smooth; marked towards the margin with numerous, fine, 

 imbricating lines of growth ; dorsal margin evenly convex, without jDosterior angle ; posterior end obtusely 

 rounded ; anterior end forming an obtuse lobe before the beak ; ventral margin inflexed, slightly sinuate. 



The broad, spatulate form, want of posterior angle, and even convexity of the surface, distinguish this from 

 every other Palaeozoic species. From the beak to the posterior end, two inches two lines, greatest length from 

 the dorsal to the ventral margin one inch one line. Communicated by Dr. Haines of Cork. 



Modiola scalaris. Phil. 



Modiola scalaris. Phil. Geol. York. 



Sp. Ch. — Transversely oblong, twice as wide as long, slightly convex ; beaks close to the anterior end, 

 which is very short and rounded ; posterior end obliquely subtruncate, rounded ; dorsal and ventral margins 

 parallel ; surface marked with distinct, narrow, regularly elevated ridges, separated by broad, flat, smooth 

 spaces. Width about half an inch. 



IMoDioLA subparallela. Povtk. 



Modiola subparallela. Portk. Geol. Eep. 



Sp. C/;. — Transversely oblong, diagonally gibbous ; dorsal and ventral margins nearly parallel ; a slight 

 sinus in the middle of the ventral margin ; anterior and posterior ends rounded, nearly equal ; hinge-line three- 

 fourths the length of the shell ; surface coarsely striated concentrically. Length six Hues, width one inch. 



LiTHODOMUS DACTYLOIDES. MCoy. (PI. XI. fig. 41). 



Sp. Ch. — Width three times the greatest depth, cylindrical; extremities obtusely rounded; beaks incon- 

 spicuous close to the anterior end ; surface marked by concentric lines of growth, which, near the beak, are de- 

 cussated by very fine, oblique, longitudinal striK. 



This is one of the most remarkable instances I know of a strong analogy existing between a fossil shell of 

 the older rocks, and a species at present living in our seas. So strong is the resemblance which the present 



