CONOCARDIUM. 
21 
description, is doubtless the same ; although Clarke, who states it to be rare in the 
Iberger Kalk, unites it with Sowerby's, and separates it from d'Archiac and de 
Verneuil's shell. 
G. clathratum, Steininger, is identified by him with d'Archiac and de Verneuil's 
shell, and also apparently with our English shells. 
The shells which Sandberger^ figures as G. aliforme, Sow., are rather perplexing. 
His figures have the appearance of being slightly idealized. While agreeing with 
ours in many respects, they are decidedly more rounded and more transverse, 
and have fewer median ribs. They seem to correspond better with G. pugnans 
than with the present form. 
It appears to me that the shell described by Barrels^ as a variety of Gonocardium 
vexatum, Barrande,^ may be a young form of this species ; for some of the smaller 
Lummaton specimens seem to correspond with it, and, though their shape some- 
what changes with their size, I see no reason for separating them from the larger 
specimens from the same place. Barrande's original G. vexatum is, however, 
distinctly different. It has a wider median region, with much more numerous ribs. 
I can find no distinguishing features in G. OMoense, Meek, which I am, there- 
fore, obliged to consider as identical. 
Affinities. — I am very doubtful whether G. Mar si, CEhlert,* is distinct from 
G. clathratum, either as originally defined or as represented by our shells. CEhlert 
distinguishes it from d'Orbigny's species as being more transverse, and as having 
the median region less flattened, more oblique, and not bounded behind by a 
stronger ridge, but passing insensibly into the posterior part. Judging from our 
specimens, many of these distinctions fail. It is true that in our fossils the 
rib of the median keel is never actually stronger than the others, but in some of 
them the keel itself is sufiiciently prominent, and considering their variability there 
seems no possibility of separating them from the Grerman form. Comparing them 
with CEhlert's figures, there seem to be some small distinctions ; as in the latter 
the superior margin seems more convex, the umbo less prominent, the shape more 
trigonal, the back more oblique and narrower. In G. Marsi, as given by Barrois,^ 
these distinctions are still more pronounced, and moreover the height is definitely 
greater and the median ribs alternate. In face of these points I do not feel justified 
in uniting the species at present. 
Miinster figures several species which evidently belong to this genus, but are 
as evidently not accurately represented. Of these, Gardium propinqmtm, Miinster,^ 
1 1853, Sandberger, ' Verst. Ehein. Nassau,' p. 257, pi. xxvii, figs. 6 a — d. 
2 1889, Barrois, ' Faun. Kalk. d'Erbray,' p. 167, pi. xi, figs. 8 a—d. 
3 1881, Barrande, ' Syst, Sil. Boheme,' vol. v, pt. 2, pi. cxcv, figs. 1, 1-3, Et. G. 
* 1887, GEhlerfc, ' Ann. Sci. Geol.,' vol. xix, p. 15, pi. i, figs. 23—31. 
5 1889, Barrois, ' Faune Kalk. d'Erbray,' p. 160, pi. xi, figs. 4:a—d. 
6 1840, Miinster, 'Beitr.,' pt. 3, p. 59, pi. xii, figs, la, b. 
