456 CARBONIFEROUS LAMELLIBRANCHIATA. 



The only other important synonym is Gonocardium ouralicum of de Vernenil. 

 That author considered that the Russian shells, even in the best state of preserva- 

 tion, always showed radiating ribs, and tliat the anterior subcyliudrical portion of 

 the valve was separated from the body by a sinus. I can state with certainty tliat 

 the latter character exists in many specimens of Gonocardium rostratum ; and the 

 former character I believe to be present or not according to the age, size, and 

 condition of preservation of the shell. Even de Verneuil does not show that his 

 shell has a rostrum. M'Ooy pointed out the identity of the G. rostratum and G. 

 ouralicum ; and I agree with every word of his observations on this subject. De 

 Koninck unfortunately never saw the rostrum, for he states {op. cit., 1885), " Elle 

 semble y etre depourvue de long rostre;" but PI. LI, fig. 7, leaves no room 

 to doubt that this process was as long as, if not comparatively longer than, in 

 any species of the genus. 



G. rostratum does differ, however, from nearly all the other species in the 

 small amount of truncation of the posterior end and the absence of a posterior 

 flat or even concave surface ; and, moreover, it appears to have had no shelly 

 fringe or flange extending backwards from the keel, which is less angular than is 

 usual in the genus. 



No other British species can possibly be confounded with this one ; but de 

 Koninck has described G. suhrostrattim, which, he says, is " much less fusiform, 

 its cordate region is much better limited, and the ornaments of the surface are 

 quite different." A fine series of this species from Settle is in the Burrows 

 Collection in the Woodwardian Museum of Cambridge. The Museum of the 

 Geological Survey at Jermyn Street also contains a fine series showing different 

 stages of growth, from the Carboniferous Limestone of Derbyshire. 



De Koninck thinks that the shell figured as Gonocardium aliforme by Romer 

 (op. cit.) should more correctly be referred to G. rostratum. This view is 

 probably correct, but the drawing is bad, and it is impossible to be absolutely 

 certain about the matter. 



CoNOOAEDiUM iRREGULARE, de Koniiicl; 1842. Plate LI, figs. 12, 13. 



Caedium irbegulabe, de Koninck, 1842. Anim. Foss. Terr. Carbonif. Belg., 



p. 88, pi. iv, fig. 14. 

 CoNOCABDiUM IRBEGULABE, d'Orbifffit/, 1851. Prodrome Paleont., vol. i, p. 132. 



— — Bigsby, 1878. Tiiesaurus Devonico- Carboiiiftrus, 



p. 303. 



— — de Koninck, 1885. Ann. Mus. Roy. Hist. Nat. Belg., 



vol. xi, p, 117, pi. XX, figs. 23—25. 



Specific Characters. — Shell small, almost equilateral, transversely triangular, 

 strongly keeled, compressed both in front and behind. The anterior wing is 



