1897.] On the Characters of Macropetalichthys. 493 
ON THE CHARACTERS OF MACROPETALICHTHYS. 
By C. R. Eastman. 
Although crania of Macropetalichthys have been known for 
more than sixty years, and have been frequently figured and 
described, the genus remains one of the most enigmatical of 
Palaeozoic fishes. Notwithstanding its abundance and gener- 
ally excellent state of preservation, circumstances which are 
conducive toward a comparative investigation, we have as yet 
only a superficial knowledge of itsstructure. In fact, it would 
not be exaggerated to assert that none of our Devonian fishes 
have been so completely misapprehended and erroneously de- 
scribed as Macropetalichthys. This will hardly be disputed when 
we recall the disagreement concerning the number of species, 
and the fact that they have been described under no less than 
five different generic titles. It is further true that sensory 
canals have been almost invariably mistaken for sutures, and 
comparisons essayed on the basis of an imaginary osteology ; 
a structure altogether distinct from the head shield, and sepa- 
rated from it by a bony wall, was mistaken for the “ cerebral 
chamber” (Newberry); a pineal foramen is stated by all ob- 
servers to be absent; and the osteology of the most familiar 
species, M. sullivanti, is still a regio incognita. 
The only species in which the arrangement of cranial plates 
has been worked out with any degree of accuracy is that rec- 
ognized as the type of the genus, M. rapheidolabis. The origi- 
nal description of this species by Norwood and Owen! is very im- 
perfect. Newberry? who examined a cast of the type specimen, 
elicited no new information regarding it; and it was reserved 
for Cope, as late as 1891, to redescribe thë type specimen as 
satisfactorily as its mutilated condition would permit. This 
historic fossil, it is sad to relate, has since been destroyed by 
fire. Cope also described in the same article a specimen of M. 
1 Amer. Jour. Sci. [2], Vol. I, feed pp. 367-371. 
1 Ibid, Vol. XXXIV, (1862), p. 
3 Proc. U. S. Nat. Museum, Vol. pel (1891), pp. 449--456. 
