ORTHOCEKATID-E. 
107 
by Phillips ; in this they are distant about ^ the diameter. The 
siphunc-le is central. The surface is ornamented with numerous 
fine, thread-like, transverse lines, in which a certain regularity of 
grouping may be observed (Phillips's specimen) ; that is, there are 
broader lines with narrower ones (two or three) between them. The 
lines have a very markedly undulating course in Phillips's type 
specimen, but they are not so represented in Sowerby's figure, and 
therefore this may not be a constant character. They are figured 
by Munster and de Koninck also as perfectly direct. 
Remarks. This species is recorded by d’Archiac and de Yerueuil, 
de Koninck, and Eichwald as occurring in Silurian (? Ordovician) 
strata, but as these authors give no figures one cannot tell what 
their fossil really is. 
Horizon. Carboniferous Limestone. 
Localities. British. Bolland, Yorkshire. — Foreign. Tournai, Bel- 
gium. 
The “ Gilbertson Collection ” in this Museum contains the speci- 
men figured by Phillips in the ‘ Geology of Yorkshire ’ (loc. cit.). 
Orthoceras dactyliophorum, de Koninck. 
1843. Orthoceras annulatum, de Koninck, Precis 6lt§m. de Geologic, par 
J. J. d'Omalius, p. 510 (not of Sowerby). 
1844. Orthoceras dactyliojihorum, de Koninck, Description des Anim. 
Fossiles de la Belgique, p. 318, pi. xlvii. f. 2, pi. xlviii. f. 7, a, h. 
Sp. Char. Shell straight. Section circular. Yery slowly in- 
creasing. Septa rather strongly convex, distant about ^ the di- 
ameter of the shell. Siphuncle central. Ornaments consisting of 
strong, obtusely rounded annulations, distant from each other rather 
more than their own width, i. e. about 3 lines, measuring from summit 
to summit. The entire surface is covered with fine, transvere riblets, 
and there are also obscure traces of longitudinal riblets. 
Remarks. The species most nearly resembling this one is Ortho- 
ceras (’‘ Cycloceras”) Icevigatum, M‘Coy, but that is described as 
having a perfectly smooth surface, that is, it has no riblets. It has 
moreover, according to de Koninck’s figures of it, a more rapid rate of 
tapering than the present species. 0. annidato-costatum, Meek and 
AYorthen (Palaeont. of Illinois, vol. ii. 1866, p. 304, pi. xxiv. flf. 3 a, 
3 5), is also an allied form, but like the last named it tapers more 
rapidly, and is besides somewhat compressed instead of circular. 
Honzon. Carboniferous Limestone. 
Locality. Kildare. 
Fairly well represented in the Collection. 
