302 



Fig. 239. Goniatites 



.<.<> /•(/ r i a in . Young 

 specimen from the 

 Naples shales of Big 

 Sister Creek. Erie Co., 

 N. Y. (after Clarke). 



Distinguishing Characters. — Ornamental lines; these begin 

 in the young shell as strong simple varices, 

 retaining their strength through the third 

 and part of the fourth volution, and be- 

 coming obsolescent on the latter part 

 of the fourth volution; on the ventral 

 side they form a deep and narrow 

 backward loop, curving forward on the 

 hyponomic ridges, and backward with a 

 broad curve on the lateral slopes ; the 

 difference in whorl-section is shown by a 

 comparison of the cross-sections (Figs. 240, 238, 236); 

 suture and umbilication as in M. intumescens. 



This species * * "has been found only in the vicinity of 

 Angola, on the Lake Erie Shore, and along Big Sister and 



Fariiham creeks, Erie Countv.*' 

 (Clarke. ) The species occurs in the 

 Naples shales. 



Goniatites (Gephyro c e - 

 RAS*) holzapfeli. Clarke. (Fig. 

 241.) (Naples Fauna, 16th Ann. 

 Rep't N. Y. State Geol., p. 87, PI. 

 VII. ) 



Distinguishing Characters.— Re- 

 sembles P.lutherim its compressed, 

 discoidal whorls and flattened, 

 grooved periphery ; differs from it 

 in being more widely umbilicated, 

 and in having the lateral saddles 

 and sublateral lobes obtuse, a con- 



Copy of Clarke's figure of the type -■•,• i • .. r. ,1 



specimen, from the Naples shales of dition characteristic of the younger 



Eighteen Mile Creek : suture of one .. 7-, , . , 



side enlarged (after Clarke). StagCS Of F. lutlWri. 



* Gephyroceras, Hyatt, •• * * includes species with discoidal .young whorls, with broad 

 and more or less flattened abdomens in the adolescent stages, and the side divergent as in 

 Manticoceras. * * The adult whorls become compressed and sub-acute in several species, 

 but retain their open umbilici, except in the most involute species. * * The depth of the 

 ventral lubes causes the septa to assume a convex aspect, but the median line remains con- 

 cave until a late stage of growth. The large lateral saddles when first formed, and until a 

 comparatively late stage in radical species, have no corresponding dorsal saddles; these 

 arise later as two minute saddles in the dorsal lobe, on either side of the annular lobe." 

 (Ilyatt : The Genera of Fossil Cephalopoda, p. 316.) 



