CONOCARDIUM. 
25 
aliformei by Goldfuss,^ but to differ distinctly from the rest of those which he 
groups with it under " var. a."^ 
The shells referred to C. aliforme by Sandberger are so similar that, allowing 
for individual variation and a little artistic idealization, both of which are apparent 
in his drawings, they may be regarded as probably identical. The chief 
differences observable are a broader rostrum, a wider median region, and more 
rounded and undulating margins. 
Affinities. — In some respects this shell presents a resemblance to G. clathratum, 
d'Orbigny, but its decidedly greater length, its smaller size, its conical shape, 
its few unequal median ribs, the closeness and fineness of its transverse threads, 
and some other points, added to a general air of similarity in all our specimens, 
induce me to regard it as a distinct species. 
The Devonian shell referred by Phillips to PI. m,inax^ (with which I formerly 
identified this species) while agreeing in its transverseness, differs specifically 
in many other particulars. It is much larger, its anterior slope is small and con- 
cave, its inferior margin is convex, its anterior keel is in front of the greatest 
height, and the ribs on the median region are much more numerous, while those on 
the posterior projection are very much larger. Prom the Carboniferous specimens 
of PI. minax, Philhps,* in the British Museum it is also certainly distinct. 
Of the species described by Barrois from Brbray three only could be con- 
founded with it. Of these, G. refiexum, Zeiler,^ is the nearest, and corresponds in 
the fineness of its concentric strise, but is distinguished by the much larger 
number of ribs (8 — 9) on the median region, the much greater convexity of the 
posterior and inferior margins, its sharper anterior keel, and its more convex 
anterior slope, which moreover according to Zeiler, but not to Barrois, has more 
serrated ribs than those of the median region. 
Gonocardium micella, Barrande,^ and G. CEhlerti, Barrois/ differ in the same 
particulars, as well as in the coarseness of their concentric strige and the greater 
distance of their ribs. 
Gonocardium retusum, Maurer,® which seems to be identical with Lichas antiquus, 
1 1834-40, Goldfuss, 'Petref. Germ.,' vol. ii, p. 213, pi. cxlii, figs. 1 h—d (only). 
Ibid., figs, a and y. 
3 1841, Phillips, ' Pal. Foss.,' p. 33, pi. xvii, figs. 50 a, i. 
4 1836, Phillips, ' Geol. Yorks.,' vol. ii, p. 210, pi. v, fig. 27. 
^ 1857, Zeiler, ' Verh. d. Nat. Vereins, Bonn,' vol. xiv, p. 48, pi. iii, figs. 4 — 8 ; and 1889, Barrois, 
' Faun. Calc. d'Erbray,' p. 164, p. xi, figs. 7 a — h. 
6 1881, Barrande, ' Syst. Sil. Boheme,' vol. vi, pi. cxcix, figs. 1, i-i6, £t. F ; and 1889, Barrois, 
' Faun. Calc. d'Erbray,' p. 162, pi. xi, figs. 5 a—f. 
7 Ibid., p. 163, pi. xi, figs. 6 a — d. 
8 1885, Maurer, ' Abhandl. Grossh. Hessiseli. Geol. Landes.,' Band i, pt. 2, p. 227, pi. ix, 
figs. 22—26. 
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