164 
NAUm-OIDEA. 
Family ACTiyOCERATIDiE. 
Genas ACTINOCERAS, Bronn ^ 
[^Cochleati, Queristedt, 1836^ (pars); ComV/^es ?, Pasch, 1837^ (non 
Lamarck) ; Conotuhularia, ,Troost, 1838 ^ (pars) ; Ormoceras, Stokes, 
1840®; Nummularia, de Koninck, 1844®; Thoracoceras (antea Melia), 
Fischer de Waldheim, 1844" (pars).] 
Gen. Char. Shell attaining to a very large size in some species ; 
straight ; elongate-conical. Section circular to subcircular. Septa 
Fig. 20. Fig. 21. 
Fig. 20. Weathered fragment of Actinoceras Bigshyi, showing the endosiphon, 
en, with some of its tubuli, t (these structures have been thickened by 
incrustations of pearl-spar) ; s, septa. Natural size. From the Black 
Biver Formation of Thessalon Island, Lake Huron. 
Fig. 21. Fragment of the same species, showing the foramina,/^ in tlie walls of 
the siph uncle, by wliich the tubuli thrown out by the endosiphon may hare 
communicated with the septal chambers; s, septa. Natural size. From 
the Cincinnati Group, Versailles, Kentucky. 
^ Lethgea Geognostica, 1837, Zweite And. Band i. p. 97. The genus Actino- 
ceras appears to have been founded solely upon Big.sby’s figures in the Geolo- 
gical Society’s Transactions, 1824, ser. 2, vol. i. p. 198, pi. xxv. S. 1, 2 (excl. 
f . 3), and while accepting it Stokes justly protests against the establishment of 
genera ‘‘ from no other materials than figures published by other persons.” 
^ De Notis Nautiliarum primariis. 
2 Bolens Palaontologie, p. 150. 
Mem. Soc. Geol. de France, tom. hi. pt. i. p. 87. 
® Trans. Geol. Soc. vol. v. pt. iii. p. 709. 
® Descrip, des Anim. Foss, de Belgique, p. 508. 
^ Bull. Soc. Imp. des Nat. de Moscou, tom. xvii. p. 755. 
