MEGAMBONIA CARBONIFERA. 133 



Dimensions. — PI. XXII, fig. 10, a loft valve, measures — 



Antero-posteriorly . . . .27 mm. 



Dorso-ventrally (largest diameter) . . 15 mm. 



From side to side (estimated) . . .9 mm. 



Locality. — Ireland: the Carboniferous Limestone of Little Island, eo. Cork. 



Observations. — I find four shells in the cabinet of Mr. J. Wright, from Little 



Island, labelled (I en-ill in. inconspicua; but I have considered the latter to represent 



Savgninolites striato-lamellosus, do Koninck, supra, vol. i, p. 398. Those shells appear 



to me to be new and I now refer them to the genus Modioli. A fifth example from 



the same locality is in the Geological Collection of the British Museum (Natural 



History). The shell is very well marked, and though at first sight it has a certain 



resemblance to 8. striato-lamellosus, de Koninck, it is more nearly triangular and 



has no escutcheon or lunulo, while radiating lines are absent on the dorsal slope. 



Genus Megambonfa, Hall, 1859. 



Megambonia, Hall, 1859. Pal. New York, vol. iii, p. 273. 



„ 1885. Geol. Surv. New York, Pal., vol. v, pt. i, LameUibr. II, 

 p. lv. 



Generic Characters. — "Shell cquivalve or sub-equivalve, very inequilateral, 

 obovoid, body very oblique ; anterior end lobed ; posterior large, constituting the 

 principal part of the shell ; beaks interior ; cardinal line short, subalate posteriorly ; 

 umbonal slope ventricose, not defined. Surface marked by fine strise of growth 

 which in some species are crossed by fine radiating striae. Hinge-line short, a 

 distinct lateral fold and groove near the post-cardinal angle. Ligament internal. 

 Anterior muscular impression large and strong, posterior impression large." 



Observations. — I have quoted Hall's generic diagnosis as given in 1885, which 

 indicates a closer affinity to Modiola than to other genera. Hitherto no shells 

 belonging to this genus have been found in Carboniferous rocks, but two specimens 

 which I refer to it have been obtained from the Limestone of Kniveton, 

 Derbyshire. 



Megambonia carbonjfera, sp. nov. Plate XXV, fig. 8. 



Specific Characters. — Shell below medium size, obliquely gibbose and obovate 

 with an anterior lobe and compressed postero-superior angle. The anterior 



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