288 



^^"^^^^ 



living- chamber twice as long as its median diameter; nn- 

 merons regular air chambers; thin, smooth septa, concavity 

 equal to an arc of IIG degrees; large straight central cylin- 

 drical siphuncle; concentric and longitud- 

 inal strife. 



lH)und "in the Hamilton group, on Lake 

 Erie Shore "* "." (Hall, type.) 



Orthoceeas subulatum. Hall. (Fig. 

 221.) (Tal. X. Y., Vol. Y., Pt. H.. p. 283, 

 Pis. XXXYHL, LXXXIY., LXXXYL) 



J}istinij;iiis]nng ( Imracters. — Straight, 

 regnlarly expanding suljulate foi'm : circular 

 cross - section : sub - cen- 

 tral siphuncle; living- 

 chamber three times as 

 long as its basal diame- 

 ter: thin, smooth septa, 

 with concavity e(]ual to 

 an arc of about 125 de- 

 grees. 



Found in the upper 

 Moscow shale, two feet 

 from the top, at Section 

 2 ( rare ) : in the Encri- 

 nal limestone, at Sec- 

 tion 5 (rare): three feet 

 below the Encrinal lime- 

 stone, at Section (J 

 ( rare ) ; and in the Stro- 

 phuncie (after Hall;, phalosia Ijcd, ill Avcry's 

 Creek (common). 



Okthocekas EXILE. Hall. (Fig. 222.) 

 (Pal. X. Y., Yol. Y., Pt. n., p. 290, Pis. 

 XXXIX., LXXXIY., LXXXY.) 



Distini>ukhing (Imvacters. — Straight, slender, regularly 

 enlarging form, with circular cross-section, and apical angle 

 of five degrees; concavity of septa e([ual to depth of 



^>«?7S;:-v.-.x, 



'■* -^■^*'f^ 



^ -• :r^ 



Fig. 223. Orthnce- 

 ras telamon. The 

 living chamber, with 

 one air chamber at- 

 tached, and basal 

 view of same, show- 

 ing position of si 



Fig. 224. (hthur,:i-as aii- 

 lax. A fragmentary speci- 

 men, from Hamburg on- 

 the-Lake (after Hall). 



