23 
DEVONIAN FAUNA. 
differs from this and our other English species in having its anterior slope much 
more rounded and its radiations finer. Allowing for the inaccuracy of the figure, 
it is just possible that Gardium semialatum, Milnster/ may be identical. The 
number and prominence of the ribs are the same, and the general shape not alto- 
gether dissimilar, though, as the posterior projection seems narrower, more pro- 
duced, and smooth, and the median region passes insensibly into the posterior, it 
may be best not to unite them without further evidence. In G. paucicostatunif 
Miinster,- the ribs are fewer, and the posterior projection larger and more definitely 
smooth. 
G. cuneus, Conrad,^ as given by Hall,^ is very similar, but differs in being 
much larger, and in having the anterior slope concave, and the median region 
much wider and passing insensibly into the posterior region. 
G. Bohemicum, Barrande,^ generally has a more rounded anterior slope, and a 
larger median region with many more ribs. One or two of his many figured 
specimens seem less distinguishable in these respects, and might, perhaps, be 
united with our shell, were it not that they are evidently variations of a species 
which is usually quite distinct. In every case the posterior sinus is much higher. 
G. deletum, Barrande,*' has a stronger anterior ridge and a concave anterior 
slope, and is a much shorter and squarer shell. 
G. artifex, Barrande,''' has a much more distinct posterior sinus, a narrower 
and generally more oblique median region, and more numerous ridges on the 
anterior slope. 
G. trigonale, Phillips, as given by de Koninck,^ has many more ribs in the 
median region, which is wider and more defined. 
Some of the medium-sized figures of Gonocardium quadrans, Barrande,® seem 
hardly distinguishable from it, but on the whole that Bohemian species seems to 
be more finely ribbed, its median region is narrower, and there is a strong sharp 
sinus between the posterior slope and posterior aliform protuberance. 
Gardium crenatuin, Steininger^" seems to be a much larger and less transverse 
1 1840, Miinster, 'Beitr.,' pt. 3, p. 59, pi. xiii, figs, la — c. 
2 Ibid., pt. 3, p. 59, pi. xiii, fig. 2. 
3 1840, Conrad, ' Geol. Surv. N. Y. Ann. Eeport,' p. 206. 
* 1885, Hall, ' Pal. N. T.,' vol. v, pt. 1, sect. 2, p. 409, pi. Ixvii, figs. 1—31 ; pi. Ixviii, figs. 1, 
4—16 ; pi. xciv, figs. 11, 12. 
^ 1881, Barrande, ' Syst. Sil. Boh^me,' vol. vi, pi. cxcvi, figs. 1 — 43 ; pi. cxcvii, figs. 1, i— 3o, and 
2, 1-20, Et. F. 
6 1881, Ibid., pi. cxcT, figs. 1, 4-6, Et. G. 
' Ibid., pi. cxcix, figs. 2, i-3b, lEt. P. 
8 1885, de Koninck, ' Ann. Mus. Eoy. H. N. Belg.,' vol. ix, pt. 5, p. 103, pi. xli, figs, 15—20. 
3 1881, Barrande, ' Syst. Sil. Boheme,' vol. vi, pi. cc, figs. 2, 1-S2, Et. F. 
1853, Steininger, ' Greogn. Beschr. Eifel,' p. 51, pi. iii, figs. 4 «, i, 5 a, h. 
