188 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



II. THE CARBONIFEROUS FISH-FAUNA OF MAZON 



CREEK, ILLINOIS. 



Of the thousands of fossiliferous ironstone nodules of Coal Measure age, oc- 

 curring at Mazon Creek, near Morris, in Grundy County, Illinois, only a small 

 percentage yield indications of vertebrate remains, and these consist princi])ally 

 of detached fish-scales. Occasionally, however, complete individuals of fossil 

 fishes, and in still fewer instances. Amphibian skeletons have been brought to 

 light, but all told the number of even tolerably perfect specimens preserved 

 in diffei'ent museums is very insignificant. Probably the two finest series of 

 Mazon Creek nodules ever brought together are the Lacoe collection, belong- 

 ing to the United States National Museum at Washington, and the S. S. Strong 

 collection, purchased by the late Prof. O. C. Marsh for the Yale Museum. 

 Shortly before the decease of Professor Marsh, nearly all of the fossil fishes in 

 the Strong collection were placed by that gentleman in the hands of the writer 

 for investigation; and more recently some additional material has been loaned 

 for the same purpose by Prof. C. E. Beecher, to whom grateful acknowledg- 

 ments are hereby rendered. 



Mazon Creek fish-scales have been exhaustively studied bj' E. D. Cope ^ anel 

 0. P. Hay,^ and the latter has also described a nearly perfect example of a 

 Palaeoniscid fish, named by him Elonichthys hypdlepis. Other Palaeoniscids 

 and Platysomids have been described by Cope,^ Newberry and Worthen,* and 

 the present writer,^ and the latter has also published descriptions of one 

 Coelacanth and two Acanthodian species.^ These citations complete the liter-' 

 ature references on Mazon Creek fishes. In the following paragraphs a few 

 new species are described, and the structure of certain Ganoids is examined 

 more in detail than has been done heretofore. 



DIPNOI. 



CTENODONTIDAE. 



Sagenodus cristatus, sp. nov. 



(Plate 3; Fig. 30.) 



Type. — Palatine dental plate ; Yale Museum. 



Upper dental plate relatively short and broad, attaining a length of about 5 

 cm. and a maximum breadth of 3.5 cm. Outer margin nearly straight; coronal 



1 Proc. Amer. PliiL Soc, VoL XXXVI., 1897, pp. 71-82. 



^ Ibid., Vol. XXXIX., 1900, pp. 9G-120. 



3 Proc. U. S. Nat. Museum, Vol. XIV., 1891, p. 462. 



^ Pal. Illinois, Vol. II., 1866, and Vol. IV., 1870. 



6 Journ. Geol. Vol. X., 1902, p. 450. 



6 Bull. Mus. Coinp. Zool., Vol. XXXIX., 1902, pp. 93-94. 



