GAXOCEPHALA. 205 



origin of species may be based, the most exemplar}- instance 

 of a transitional form, on the derivative hypothesis, of an air- 

 breather from a water-breather. \Yhether the conditions of 

 such derivation be external and impressive, or internal and 

 genetic, and the degree in which those conditions may com- 

 bine, if both concur in the work, is a problem needing much 

 future observation, and the acquisition of a large amount of 

 facts yet unknown. Those which have been acquired since 

 Lamarck's speculations on the degrees in which outward 

 influences might impress changes in structure, have contri- 

 buted to their banishment. But a refutation of guesses at 

 the mode in which one form, or grade of animal structure 

 may be changed into another, leaves the possibility of deri- 

 vation of one form from another open to the mind of every 

 unbiassed explorer of the laws of animated nature ; and no 

 fact, old or new, ought to be dismissed until its relations to 

 the great question have been completely and impartially con- 

 sidered, with all the power of thought winch the naturalist 

 can bring to bear upon it. 



Genus Kaxiceps. — In about the centre of the great car- 

 boniferous basin of Ohio, United States, at the mouth of the 

 " yellow creek," is a seam of coal 8 feet in thickness, the lower 

 four inches of which is " cannel coal." In this has been found 

 the skull, part of the vertebral column, scapular arch, and fore 

 limbs of a reptile, referred by Professor \Yyman* to the batra- 

 chian sub-class, under the name of Raniceps. Two closely- 

 allied fossils, also referred to Batrachia, have been found in 

 the same formation and locality. 



Genus Dexdrerpetox. — This is founded on some small 

 bones discovered in the hollow of the trunk of one of the trees 

 (Sigillaria, 2 feet in diameter), wholly converted into coal, the 

 stumps of which stand erect in a coal-field of Xova Scotia. 

 The genus is batrachian, with close affinities, from the plicated 



* American Journal of Science and Arts. March 1857. 



