188. BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 
Il. 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 principally 
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 different 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 by E. D. Cope! and 
O. P. Hay,” and the latter has also described a nearly perfect example of a 
Palaeoniscid fish, named by him Hlonichthys hypsilepis. 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.6 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. Phil. Soc., Vol. XXXVI., 1897, pp. 71-82. 
2 [bid., Vol. XXXIX., 1900, pp. 96-120. 
3 Proc. U. S. Nat. Museum, Vol. XIV., 1891, p. 462. 
4 Pal. Illinois, Vol. II., 1866, and Vol, IV., 1870. 
6 Journ. Geol. Vol. X., 1902, p. 450. 
® Bull. Mus. Comp. Zool., Vol. XXXIX., 1902, pp. 93-94. 
