266 CARBONIFEROUS LAMELLIBRANCHIATA. 



Cardiomorpha Sowerbyi is founded on a fragmentary valve, and it is stated 

 " cetteespece est plus allongee que le Cardiomorpha globata" — not a very definite 

 specific characteristic when a large portion of the anterior part of the shell is 

 wanting. There is a fine series of specimens of G. orbicularis from the Limestone 

 of Ardlaman, co. Limerick, in the collection of the Geological Survey of Ireland, 

 showing the shell in all stages of growth. 



I figure a well-preserved example of the hinge of this species, which was 

 presented to me by Professor G. De "Walque of Liege, fig. 4, PI. XXII, from the 

 Carboniferous Limestone of Belgium. 



Cardiomorpha ventricosa, M'Coy, 1844. Plate XXIII, figs. 1 — 4. 



Cardiomorpha ventrtcosa, M'Coy, 1844. Syn. Carb. Foss. Irelaud, p. 56, pi. 



xiii, fig. 3. 



— oblonga (pars), Morris, 1854. Cat. Brit. Foss., edit. 2, p. 191. 



— — Griffith, 1S60. Journ. Geo!. Soc. Dublin, vol. ix, p. 91. 



— — (pars), de Koninck, 1885. Ann. Mus. Hist. Nat. Belg., 



vol. xi, p. 11. 



— — Etheridge, 1S88. Brit. Foss., vol. i, Palaeozoic, p. 281. 



Specific Characters. — Shell of only moderate size, very obliquely ventricose, 

 produced downwards, so that the antero-posterior diameter is shorter than the 

 others in all except very large examples ; shape very irregular. The anterior end 

 is very short, deeply excavated above, just below the twisted umbones, but else- 

 where regularly swollen. The anterior border is curved and very short. The 

 inferior border descends downwards and somewhat backwards, passing at its 

 posterior and lowest portion into the posterior border with a blunt curve. The 

 latter border is extended and very bluntly curved, joining the hinge-line above 

 without any marked break. The hinge-line is arched, the posterior part pro- 

 duced. The umbones are large, gibbose, somewhat compressed laterally, much 

 raised above the hinge-line, twisted forwards, with their apices markedly pro- 

 sogyrous, being curved on themselves, and very anterior in position. The 

 umbonal swelling is prolonged obliquely across the shell to the postero-inferior 

 angle, becoming somewhat flattened in its progress across the shell. Above 

 this swelling, which occupies a very large portion of the valve, the shell is com- 

 pressed so as to form a gradually flattened slope towards the hinge-line, which lies 

 in the centre of an elongate groove between the two expanded valves. Below 

 the oblique swelling the valve is somewhat flattened and compressed into the 

 inferior border. 



