THE 
AMERICAN GEOLOGIST. 
Vol. XXX. NOVEMBER, 1902. No. 5. 
THE PRESERVATION OF MUSCLE-FIBRES IN 
SHARKS OF THE CLEVELAND SHALE. 
By Bashford Dean, Columbia University, New York. 
PLATES VIII AND IX. 
In fossils of vertebrates, fragmentary as they are, 
soft parts are sometimes preserved with startling clearness. 
jNIiiscles and integnmental webs are well known in a" number of 
grgups, and the student of palseanatomy has even collected con- 
vincing data regarding the nature of such frail organs as soft- 
walled viscera and spinal cord. Muscles, especially, are apt to 
be well preserved, even to the details of their individual fibres. 
Favorable instances of the fossilization of muscle fibres are 
by no means uncommon in the fishes of the lithographic stone, 
as Reis has pointed out. Here in the case of the ganoid 
f '»(///uj,* he has described the fibres and their ''reizende Stria- 
tion." as .so well preserved as to give an "ideale Bild der ]\Ius- 
Ixelstructur," — although this optimistic conclusion may not be 
shared by a reader on accoiuit of Reis's indifferent figures. And 
even in less finely grained sedimentary rocks examples are not 
lacking, both here and abroad, of well preserved soft tissues. In 
the case of an American matrix the Cleveland shale deserves es- 
pecial mention, since it will no doubt provide many important 
facts regarding th.e intimate characters of the Devonian verte- 
brates. The reader may recall, for example, that it was in this 
shale that Newberry!' first suggested the preservation of trans- 
*Die Coelacanthinen, m. bes. Beriicks. d. Gatt. d. weiss. Jura Bay- 
erns. Palieonto^raphica. Bd. XXXV, Taf. II. 
tMoh. X\I. U. S. Geolog. Surv. 
