20 Tate — List of Irish Liassic Fossils. 



submedial, prominent, broad, high, and incurved. Ornamented with concentric 

 striae, varying in the degree of fineness ; and radiating striae, which are very 

 fine, not distinctly visible without the aid of a magnifier, excepting on the an- 

 terior concave area. The striae merge into impressed circular spaces on the 

 superior margin of the transverse striae, so that the surface, when viewed in 

 certain positions, appears to be regularly punctated. Length, '35 inch ; 

 breadth, "5. 



This species is not comparable with any of the Liassic ArcidcE; its peculiar 

 ornamentation separates it from C. cucullata, Goldfuss. 



Geological Position — Upper part of Lower Lias, Ballintoy, Co. Antrim 

 (Portlock, R. T., &*c), where it is very abundant. 



Dedicated to my esteemed friend the Rev. John Grainger, A.M., the 

 first President of the Belfast Naturalists' Field Club. 



19. MYTILUS subtilis, nov. spec, Plate I. fig. 14. 



Shell elongated, reniform, concentrically plicated and ornamented with 

 closely-set radiating incised lines, which are visible only with the aid of a 

 magnifier ; dorsal margin curved ; ventral margin sinuated ; umbones approxi- 

 mately terminal, prominent, small, incurved. 



Geologial Position. — Lowermost beds of the Lower Lias, Cave Hill, 

 Belfast ; very rare (S. A. Stewart). This species has the general form of M. 

 nitidulus, Dunker, but is more cuneiform than that species, which does not 

 possess the radial ornamentation. 



20. Myoconcha oxynoti, Quenstedt, Jura, t. 13, fig. 34. 



A single valve of a narrow cylindrical Myoconcha, forming part of the col- 

 lection in the Belfast Museum, displays the internal characters, but as the ex- 

 terior is unobservable, the shell cannot satisfactorily be referred to any species. 

 Terquem describes a small species from the Lower Lias, and Quenctedt figures 

 the internal cast of another form from the same formation, under the denomina- 

 tion of M. oxynoti. 



The test of the Ballintoy specimen is very thin, and from the interior sur- 

 face it is judged that the exterior is marked with concentric corrugations and 

 fine lines of growths. The apparent absence of radiating lines removes it from 

 M. inclusa, Terquem, and, as it agrees in shape with M. oxynoti, Quenstedt, 

 I refer it to that problematical species. 



Breadth, 1-4 inch ; length, -3 inch ; thickness, '1 inch. 



Geological Position. — Zone of " Belemnites acutus," Ballintoy. 



21. Myoconcha psilonoti, Quenstedt, Jura, t. 4, fig. 15 (1858). 



? Myoconcha scabra, Terquem & Piette, Pal. de l'Est de France ; t. 9, 



figs. 4-6 (1865). 

 ? Myoconcha scalprum, et M. spatula (pars) D'Orbigny, Prodromus, 



Vol. I, p. 218 (1850). 



