CKPHALOPOl \ Wi 



ra. prr..n | 



separated by furrows of equal \\i.|tli. sutures regular and lyiuj; in the 

 hori/ontal furrows septa deeply concave and regular. ;in. I -uiface markings consisting 

 of tine, do-ely-set longitudinal linos slightly alternating in size. 



These are characters agreeing with the early description-. cited, and >er\v to 

 dMinnui-li the species from Orthoceras />ilin<'<itnin. in which the shell expands more 

 rapidly and the concent IH Mn.r, which are here obscured or absent, are conspicuously 

 developed. 



and Ittfalily. In the Trenton shale* at Minneapolis, Minnesota; also at McGregor, Iowa. 

 Mmtenm RtffitUr, No. 82UO. 



OKTHOCERAH PKRKOTI, *i>. nov. 



I'l.ATE LIV. F10S, 4 and &. 



Shell moderately large, very gradually expanding. Cross-section broadly 

 MI I. elliptical, nearly circular. Surface covered by closely-set annulations about 

 J mm. in width, separated by somewhat narrower transverse furrows. Sixteen of 

 these annulations, of equal size and at regular interspaces, occur in a length of 

 41 mm. These ridges and furrows are crossed by a double series of vertical elevated 

 lines alternating in size, upon the summits of the annulations being very conspicuous 

 and developed into lamellar expansions. This character (one secondary lamella 

 between each two primary lamellae) is maintained over the entire surface, apparently 

 without the intercalation of other series. Where best preserved, the surface affords 

 no evidence of concentric lines. Sutures regular and transverse; septa evenly 

 concave, moderately deep; sipho small and central. 



The specimen showing the above characters is a well-preserved siliciBed 

 fragment retaining the exterior with unusual delicacy. Its length is 50 mm., its 

 greatest width 30 mm., and its minor axis at the same plane 26 mm. The species is 

 allied to Orihocerns olorus Hall, but its distinguishing features will be found in the 

 closer annulations and the different composition of the ornament. 



Formation and /oco/Uy.-In the Hudson River group at Granger, Minnesota. 



OKTHOCERAS LESUKURI, sp. nov, 



PLATE LIU. no. 4: I' LATE I.V. FI08. mat 9. 



Shell rather small, slender: Mil>.'lli[.tical in cross-section. Surface covered with 

 numerous fine, nearly transverse or very slightly oblique unuulations, which are 

 narrow at the base, abruptly elevated, sloping equally above and below, and ~> -para- 

 ted by grooves somewhat broader than the aimulation- themselve-. The latter 

 make a very slight backward curve on the dorsal and ventral Mirfaces, with a broad 



-50 



