ACirS-OCERATID^. 
171 
Eepresented by a very fine series of examples, including tbe 
types figured by Bigsby and Stokes. A specimen from tbe Bed 
Eiver, Minnesota, "^as presented by M’. Calwell, Esq. ; and another, 
collected by Dr. Hector, near Lake Winnipeg, Tvas transferred from 
the Museum of Practical Geology. 
Actinoceras Beloitense, Whitfield. 
1840. Actinoceras Bigshyi, Stokes (pars), Trans. Geol. Soc. ser. 2, 
Tol. T. pt. 3, p. 707 ; ibid. ser. 2, toI. i. pt. 2, 1824, pi. xxv. f. 3. 
? 1843. Actinoceras JRicTiardsoni, Castlenau, Syst. Sil. de I’Amerique 
Septentrionale, p. 30, pi. rii. if. 1, 2. 
1868. Orthoceras {Ormoceras) Backii ?, Meek Worthen, Geol. Surv. of 
Illinois, Tol. iii. p. 298, pi. i. f. 4. 
1874. Orthoceras {Ormoceras) BacJci?, Barrande, Syst. Sil. de la 
Boheme, toI. ii. Texte iv. 1877, p. 264, pi. cccclxxiv. f. 11. 
1877. Oiihoceras {Actinoceras) Behitense, Whitfield, Annual Deport 
Geol. Surv. of Wisconsin, p. 97. 
1882. Orthoceras {Actinoceras) Behitense, Whitfield, Geol. of Wiscon- 
sin, Tol. iv. pt. iii. p. 226, pi. riii., pi. x. if. 9, 10. 
Sp. Char. “ Shell large and robust, subfusiform, moderately ex- 
panding to a diameter of about four inches, then more gradually 
decreasing in size to the aperture. Section oval in all the examples 
noticed, and usually a little more flattened on one side than on the 
other, with the siphuncle submarginal on the flattened side. Septa 
shallow and not often symmetrically arranged, from seven to eight 
chambers occupy a length equal to the diameter of the largest of 
the number measured; towards the outer portion of the shell 
the septa become more crowded, and just below the outer chamber 
are sometimes less than half the usual length. Siphuncle large, 
strongly beaded within the chambers, with an inner core, in the 
casts, having radiating filaments [the tubuli of the endosiphon] 
extending to the centre of the bead in each chamber. Surface of 
the shell unknown.'*’ {Whitfield.) 
Bemarh's. The identification of one of the specimens figured by 
Bigsby with A. BeJoitense confirms the view held by Stokes that 
there might be more than one species figured on Bigsby’s plate. 
Hone of the test remains in any of the examples in the Museum 
Collection, and the septa have been removed by solvent action, leaving 
narrow intervals between the casts of the chambers. The specimens 
from which Prof. Whitfield drew up his description of the present 
species were derived from the Trenton Limestone (buff beds) near 
Beloit, Wisconsin. 
Horizon. Black Eiver ( = Llandeilo Limestones?). 
Locality. Thessalon Island, Lake Huron. 
Fairly well represented in the CoUectiou. 
