THE MISSISSIPP1AN PERIOD. 521 



but at the same time they retained many Devonian features. Not a 

 few Devonian species may be named as the probable direct ancestors 

 of Kinderhook species, as ; for example, Cyrtina hamiltonensis, as the 

 parent of C. acutirostris (Fig. 235, m); Spirifer disjunctus, of S. mari- 

 onensis (Fig. 235, I); Athyris spiriferoides, of A. hannibalensis. A few 

 species believed to be identical with Devonian forms were also present; 

 indeed the Devonian resemblances (see Fig. 235, k) are so strong that 

 the earlier paleontologists referred the Kinderhook to the Devonian, 

 classing it with the Chemung. 



Other features. — The molluscan contingent was prominent in the 

 Kinderhook faunas. The pelecypods alone have a larger number of 

 species than either the echinoderms or brachiopods. They are especi- 

 ally abundant in some of the arenaceous beds (Fig. 235, q, r, and s). 

 Among them are species indistinguishable from those of the Waverly 

 fauna that inhabited the gulf east of the Cincinnati island. The gas- 

 tropods were less abundant, but among them the capulids, a group 

 that was conspicuous among the gastropods of most Devonian epochs 

 were the most common (Fig. 235, a, b, c, and d). The chief repre- 

 sentatives of the cephalopods were the goniatites (Fig. 235, i and j), 

 and although they are generally rare, they show, in the genus Prodro- 

 mites, a notable advance over any of their known Devonian ancestors, 

 in the more highly complicated lobing of the suture. Trilobites were 

 few and small (Fig. 235, h). Their high stage of ornamentation had 

 passed, the clay of their final disappearance was drawing near, and 

 they assumed a sober and subdued aspect. The corals (Fig. 235, g), 

 though less abundant than in the preceding epochs, were represented 

 by a considerable number of forms, among which the cup-shaped type 

 was most common. 



Though without striking characteristics, the fauna represented 

 a notable stage in the evolution of distinctive Mississippian features. 

 It was essentially indigenous, and may be regarded as a transition 

 stage from the late Devonian to the typical Mississippian fauna repre- 

 sented in the following epochs. 



northern Illinois. Pelecypoda: q, Macrodon missouriensis (M. and G.); and r,Gram- 

 mysia hannibalensis (Shum.), both of which have close Devonian relationships; 

 s, Pernopecten cooperensis (Shum.), a species very characteristic of certain of the 

 higher horizons in the Kinderhook. Vertebrata: t, Tooth of Cladodus springeri 

 St. J. and W. ; and u, Tooth of Pristicladodus springeri, St. J. and W., the sharp 

 cutting teeth of sharks; v, spine of Acondylacanthus gracilis St. J. and W. 



