1918] The Ottawa Naturalist. 125 



to be narrower than the other vertical ridges. A very narrow border. 

 Fig. 33 C, extends around the entire carapace, excepting, of course, 

 along the dorsal line. All four vertical ridges' are abruptly elevated 

 to a height varying from one-tenth to one-eighth of a millimeter. Very 

 abundant in thin limestone layers, about half a centimeter in thickness, 

 interbedded in the shales, and in much smaller numbers in the shales 

 themselves, about a mile and a half north of the store of J. B. Stratton, 

 along the lake shore. 



Faunal Correlations. 



Lithologically, the cherty, light-brown or light-blue Richmond 

 limestone, forming the upper part of the section along the eastern shore 

 of Little Bay de Noquette, resembles the cherty Richmond exposed one 

 and a half miles southwest of Kagawong, on the road to Gore Bay, on 

 Manitoulin island. Archinacella kagawongensis is common to both 

 localities, but no conclusions can be based upon this species alone. 

 Among the more significant fossils found in the cherty Richmond of 

 the Michigan locality are Lichenoerinus tiiberadatus and Dinorthis 

 subquadrata; the first is known only from the Whitewater member of 

 the Richmond in the typical Cincinnatian areas, while Dinorthis sub- 

 quadratd occurs both in the Liberty and Whitewater members. 

 Chasmops breviceps is known by me only from the Liberty member, 

 although listed by Bassler also from the Waynesville. If Clionychia 

 angusta is closely related to Clionychia excavata, then the occurrence 

 of the latter in the Whitewater member should be noted. Apparently 

 this cherty Richmond limestone may be correlated provisionally with 

 the post-Waynesville portion of the typical Richmond section. 

 Helicotoma brocki has been known hitherto only from the lower, or 

 Waynesville member of the Richmond section on Manitoulin island. 

 Strophomena neglecta is known chiefly from the upper third of the 

 Waynesville member, although characteristic specimens occur occasion- 

 ally in the, Whitewater member, especially in the vicinity of Richmond, 

 Indiana. The presence of Amphilichas cucullus is merely another 

 instance of the occurrence in the Richmond, with very little change, of 

 a characteristic Trenton species. It is very evident that, while the 

 Cynthiana, Eden, and Maysville invasions were taking place in. the 

 states bordering on the Ohio river, a large part of the Trenton fauna 

 was able" to maintain itself in some other area, as yet unrecognized, 

 and from this area it was able to make a second incursion into the area 

 surrounding Cincinnati. Something similar appears to have taken 

 place in case of the Kimmswick limestone and the upper Richmond 

 in northern Michigan. 



The more significant fossils in the argillaceous Richmond lime- 

 stones on the eastern shore of Little Bay de Noquette include 

 Hebertella alveata and Platystrophia acutilirata, from the Liberty and 



