187 
Dimensions. — One of the specimens from which I gathered these 
specific characteristics is about six centimetres long, and nine broad. Another 
is only about four and a half centimetres long by five and a half broad, with 
a thickness of twenty-three millimetres. 
Relations and Differences. — Mr. T. Davidson was right in following 
the example of Mr. J, Morris in considering S. rotnndatus and S. pinguis, 
merely varieties of the same species. The numerous figures given by him 
strengthen tlie evidence which proves that one of the varieties insensibly 
merges into the other, and possesses no distinctive characteristics sufficient to 
justify their sej)aration. S. Clarkei has very much in common with S. pinguis 
especially in the matter of its ornamentation. It is, however, easily distin- 
guished by its elliptical form and by the complete absence of the longitudinal 
furrow dividing the dorsal ridge of S. pinguis. 
Horizon and Localities. — S. pinguis is one of the most abundant 
species in the Middle Carboniferous Limestone. It has been found in Belgium 
at Waulsort by M. Dupont ; and is very common at Millecent and Little 
Island, and at Malahide, Ireland. Mr. W. B. Clarke found it at Glen William 
and Burragood. 
Spiiufee, convolutus, J. RhilUps. 
PI. XII, Pig. 2 and PI. XIII, Pig. 3. 
Spirifera convoluta, J. Phillips, 183G, Geol. Yorkshire, II, p. 217, pi. 9, hg. 7. 
,, rlionihoidea ? Idem, 1836, Hid., p. 217, pi. 9, fig. 9, 10. 
Spirifer convolutus, L. G. dc Koniuck, 1813, Descr. Anim. Poss. Terr. Carh. Belg., p. 
217, pi. 17, fig. 2. 
P. M‘Coy, 1841, Synop. Carh. Poss. Ireland, p. 130. 
G. Sowerby, 1811, In Darwin’s Geol. Obs. Vole. Islands, p. ICO. 
J. Morris, 1815, In Strzelecki’s Phys. Descr. N.S. Wales and V. D. 
Land, p. 282, pi. 17, fig. 6. 
P. M‘Coy, 1817, Ann. Mag. Xat. Hist., XX, p. 233. 
J. D. Dana, 1819, Geol. Wilkes’ U. S. Explor. Exped., p. 685, pi. 2, 
fig. 3. 
L.-G. de Koninck, 1859, Mem. Soc. Eoy. Sci., XVI, p. 30, pi. 2, fig. 
7 and 8. 
Spirifera convoluta, 
„ avicula, 
Spirifer ,, 
Spirifera avicula, 
f^Spirifer vespertilio, 
„ convolutus, 
2 c 
