248 On the Systematic Position of Cheirole^is. 



be classed along with PaheoniscuSj Pygopterus^ OxygnathuSy 

 Ct/cIojytychiuSy and other genera which constitute the long- 

 extinct family of Palieoniscida?, So close indeed is the corre- 

 spondence between the general organization of CheiroJepin and 

 of Pahi'oniscuSj that at most only tiie distinction of a separate 

 '' subfamily " can be accorded to it, in virtue of the peculiarity 

 of its scales. Though the precursor of a numerous tribe of 

 most interesting iishes in the Carboniferous and Permian eras, 

 and which finally disappear with the Lias, Cheirolepis stands 

 alone in the Devonian fauna, so far as that has been as yet 

 revealed to us*; and no peculiarity of its structure throws the 

 smallest additional light on the evolution of the group to which 

 it belongs ; for the absolute divergence in all other points 

 of structure utterly excludes the idea that its minute scales 

 betray any special affinity to the Aeanthodians, while the 

 correct determination of the plates, which have been mistaken 

 for jugulars, equally forbids any association of it with the 

 "contemporaneous PolypteridEe." 



EXPLANATION OF PLATE XVIL 



Fiy. 1. Represents the mandibles and branchiostegal rays of both sides 

 of Cheirolepis Cummitigice, also the right maxilla andpart of ther 

 circumocular ring. From a specimen from Letheu liar, in the 

 collection of the Earl of EnniskiUen. 



Fig. 2. Both interclavicular bones, with the left clavicle and the lower 

 extremity of the right clavicle. From a specimen from Cro- 

 marty in the Hugh-Miller collection, Edinburgh Museiun. of 

 Science and Art. 



Fi(i. .3. Outline of the shoulder-girdle and its component bones, restored. 



Fiy. 4. A small portion of the edge of the superior maxillary bone, niag- 

 nitied two diameters. The outer row of small teeth is exhibited, 

 also one of the larger ones and the broken stump of another. 

 Hugh-Miller collection. 



Fi(j. o. Portion of the dentary bone of the mandible of another specimen. 

 Along one half of the bone the outermost edge has been broken 

 away, thus carrying off tlie small ones and exhibiting the inner 

 row of larger teeth ; along the other half this edge remains, 

 and shows some of the small teeth, while the continua- 

 tion of the row of large ones is concealed by the matrix. The 

 working-out of the small teeth has not been so successful here 

 as in the preceding specimen. 



Fig. 6. Vertical transverse section of a small portion of the lower lobe 

 of the caudal fin, magnified two diameters. 



Fig. 7. Restored outlines of some of the bones of the side of the liead. 

 The radiating lines on some of the bones are those which, on 



* With the apparent exception of four species of Acrolepis, described 

 by Eichwald from the " Old Red ' of Russia (' Lethaja Rossiea,' vol. i. 

 pp. 1578-1581). 



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