310 
NArTILOIDEA. 
? 1852. Cyrtoceras rngosum, Giebel, Fauna der Vonvelt, Band iii. 
Abtli. i. p. 207. 
1857. Amplexus ornatus, Eichwald, Bull. Soc. Imp. des Xatur. de 
Moscou, p. 176. 
1860. Cycloceras ornatum, Eicbwald, Lethfea Bossica, vol. i. Seconde 
Sect, de I’Ancienne Periode, p. 1234, pi. xlvlii. ff. 13, a, b. 
1867. Cyrtoceras rugosum ?, Trautschold, Bull. Soc. Imp. des Xatur. de 
Moscou, vol. xl. p. 44. 
1880. Cyrtoceras rngosum, de Koninck, Faune du Calc. Carbonifere de 
la BelgUlue, p. 31, pi. xxxiii. ff. 8, a, b. 
S]). Char. Shell slightly curved, slowly tapering, nearly circular 
in transverse section. Siphuncle close to the margin on the convex 
curvature of the shell. The surface ornaments consist of distant, 
transverse, rounded, somewhat waved annulations ; these are crossed 
by about thirty close-set longitudinal ridges which cross the 
annulations and the interspaces, causing the annulations to be 
distinctly nodose at their junction with the ridges. There are 
indications also of fine transverse lines between the ribs, which 
have also a nodose character at their intersection with the lon- 
gitudinal ridges. 
Remarl's. This species may be readily distinguished from M. 
rugosum by the greater distance of its annulations. 
Horizon. Calcaire Carbonifere de Vise ; = Carboniferous Limestone. 
Locality. Vise, Belgium. 
Represented in the Collection by two examples. 
b. Endogastric. 
Cyrtoceras (Meloceras) arachnoideum, de Koninck, sp. 
1844. Cyrtoceras reticulatum, de Koninck, Descrip, des Anim. Fossiles 
du Terr. Carb. de la Belgique, p. 529. 
1851. Cyrtoceras araclmoideum, de Koninck, ibid. Suppl. p. 707, 
pi. lix. ff. 6, a-c. 
1852. Cyrtoceras reticulatum, Giebel, Fauna der Vorwelt, Band iii. 
Abth. i. p. 209. 
1880. Cyrtoceras arachnoideum, de Koninck, Faune du Calc. Car- 
bonifere de la Belgique, p. 37, pi. xxxiii. ff. 14, a, b. 
Sp. Char. Shell small, somewhat more curved in the apical 
portion than in the rest of the shell ; apex acutely pointed. 
Transverse section circular. Septa shallow, the last distant from 
each other about one line. Body-chamber occupying about one 
third of the total length of the shell. Siphuncle very slender, 
situated near the concave side at one third of the distance across 
the dorso-ventral diameter. The surface is ornamented with a 
