NO. 2177. FOSSIL FISHES IN NATIONAL MUSEUM— EASTMAN. 273 



possible to recognize faint traces of the squamation, the scales appear- 

 ing to be very small and covered with delicate longitudinal striae. A 

 portion of the lateral line scale-row is indicated by characteristic 

 raised markings in the posterior part of the trunk, but the caudal 

 extremity is not distinctly shown. Apparently the tail tapered 

 gradually to a point, without being produced into a supplementary 

 caudal fui. The sum total of morphological features presented by 

 this peculiar genus and species is of extreme interest. 



Formation and locality. — Coal Measures; Mazon Creek, Illinois. 



Family PALAEONISCIDAE. 



The earliest representative of this family, and of primitive sturgeons 

 generally, is the genus Chcirolepis, remarkable for its small-sized 

 squamation. A single species is known from the Devonian rocks of 

 North America, described by Whiteaves as Chdrolejns canxidensis. 

 Three species of Palaeoniscus have also been founded upon isolated 

 scales occurring in the Upper Devonian of New York State. These 

 have been named P. antiquus and P. reticvlatus Williams, and P. 

 devonicus Clarke, but they are more properly assignable to Rhadinich- 

 ihys. 



Genus RHADmiCHTHYS Traquair. 



This genus, apparently indicated by isolated scale patches in the 

 Upper Devonian rocks of this country, and represented by several 

 species in the Lower Carboniferous of New Brmiswick and the United 

 States, persists as late as the Pemisylvanian in this country. One 

 species, R. deani, occurring at the base of the Waverly, is remarkable 

 for having yielded the first information we possess concerning the 

 organization of the brain and internal ear of any fossil fish. Since 

 the beautifully presei-ved bram structure of this species was first 

 described,^ similar remains have been found in the Coal Measures near 

 Lawrence, Kansas,- and less well-preserved specimens are also con- 

 tained in the collection of fossils from the Caney shale of Oklahoma, 

 already referred to. 



One of the specimens from the latter locality showing the internal 

 structure of the head of a small Palaeoniscid, presumably of Bhadi- 

 nichtJiys, is catalogued as No. 8111, and another showing the greater 

 part of a dentigerous mandible bears the number 8112. 



1 Ann. Kept. Iowa Geol. Surv., vol. IS, 1908, pp. 265-272. 



2 Twenhofel, W. H., and Dunbar, C. O. Nodules with fishes from the Coal Measures of Kansas. Amer. 

 loum. Sci., vol. 38, 1914, pp. 157-163. Moodie, R. L. A new fish hrain from the Coal Measures of Kansas, 

 with a review of other fossil brains. Joum. Comp. Neurology, vol. 25, 1915, pp. 135-181. 



65008°— Proc.N.M.vol.52— 17 18 



