CONOCARDIUM. 
27 
especially as they are not very perfect. At the same time there is a general 
similarity between them which shows that they all belong to one species. 
It appears to me that there is every reason to believe that this species is the 
true Bucardites hystericus of Schlotheim. His figure exactly corresponds in 
every particular with one of ours (fig. 7), Our other examples seem less globose 
shells, and have a larger anterior slope ; but their similarity in gape, ornament, 
and other points makes it impossible to separate them. 
Clarke, who has had the opportunity of examining Schlotheim's original 
example, considers that PI. trapezoidalis, F. A. Romer, is undoubtedly identical 
with it. From Romer's figure it appears squarer and more produced at the postero- 
inferior part; but, as it seems similar in other respects, I have treated it as 
synonymous on Clarke's authority. 
Cardium paucicostatum, Miinster, seems to correspond in the coarseness, 
shape, and comparative smoothness of its ribs, and the absence of ribs on its 
posterior aliform projection. It certainly differs in shape, and seems smoother 
than the English shell, but this may perhaps be due to the evident inaccuracy of 
Miinster's drawing. 
Affinities. — This species comes so close to G. clathratum that I have been in 
doubt whether to regard it as more than one of its varieties. There seem, how- 
ever, to be several distinctive features which go to prove that it is a separate 
species. Thus the gape is much wider and larger ; the ribs are coarser, and those 
on the posterior region are very square, close, and flat, and their interspaces very 
narrow and deep ; the transverse ornament does not consist of regular raised 
threads, but of ordinary indistinct growth-lines ; and the aliform posterior 
projection is almost smooth, instead of being ribbed. I think that these differences 
are too great to be accounted for by the local conditions under which the sedi- 
ment at Chudleighwas formed. 
Com cardium hifurcans, Barrande,^ differs from it in its narrower and more 
distant ribs, the strength of its anterior keel, and the greater concavity of the 
cordiform slope. 
5. CoNOCAEDiUM Phillipsii, d'OrUgnij. 
1840. Caedium alifoeme, Sowerhy. Geol. Trans., ser. 2, vol. v, pt. 3, pi. Ivi, 
fig. 2. 
1841. Pleueoehtnchtts minax, Phillips. Pal. Foss., p. 33, pi. xvii, figs. 50 a, h. 
1849. CoNOCAEDiTJM Phillipsii, ffOrUgny. Prodrome, vol. i, p. 80. 
1854. — MiNAX, Morris. Catal. Brit. Foss., p. 195. 
1889. PiEXTEOEHYNCHTJS MiNAX, Etheridge. Foss. Brit., vol. i, Pal., p. 162. 
1 1881, Barrande, ' Syst. Sil. Boheme,' vol. vi, pt. 1, pi. ccii, figs. 4, i-4, fit. E. 
