144 Annals of the Carnegie Museum. 



ward position of the dorsal fin, hut I do not think it couhl l)e classed 

 with Rcdficld's genus Catoptcnis. The smooth charactei of the scales 

 in your American specimens is the most distinctive mark I see as 

 com])ared ^\ith the PakTonisci of the Kupfer Schiefcr, Zechstein, and 

 Magnesian Limestone, all the species found in these two formations 

 having the scales more or less striated and serrated on the posterior 

 margins. This character would, ho\ve%er, ajjijroxinuite them to the 

 Coal Measure species, where the scales are all smooth, except in those 

 from the Burdi House. The tails are certainly less prolonged in the 

 upper lobe than any of the Palaouisci I am accpiainted with. 



" Believe me, Sir, 



" Yours truly, 



"Philip Grey Egerton." 



Observations on the Genus Catopterus. 



P)csides the tyiu'-si)ecics, C gracilis Redfield, writers have hitherto 

 witliout exception recognized at least one other valid member of the 

 genus, namely, C. rcdfiehli Egerton. The original description states 

 merely that this is a deeper-bodied fish than the tyi)e, and "with 

 scales not so long in proportion to their depth" (Egerton, loc. cit., 

 ]). 278). It has been observed by subsequent authors, however, that 

 in form and proportions of body the two species are very similar, and 

 in fact intergrade to such an extent that these characters alone are 

 an insufficient criterion for separating them. One may speak of a 

 deeper-bodied variety, and a less deep-bodied, or slenderer variety, 

 but the distinction is not a trenchant nor a natural one, since it depends 

 almost altogether upon varying degrees of mechanical compression 

 and deformation. The fact was clearly recognized by Newberry^ in 

 the case of one of Redfield's cotypes of C. gracilis, which, although the 

 body has slender proportions, was nevertheless conceived by this 

 author to have been a verticall>- compressed example of the broad form, 

 and for this the name C. redficldi was suggested by Sir Phillip Egerton. 



Two examples belonging to the Carnegie Museum and illustrated 

 in plates XXX and XXXI, are instructive as showing that appearances 

 may be very deceptive as to the natural contour of the body. For 

 these specimens have been so folded over and then flattened as to 

 display a larger number of scale-rows than I)elongs to a single side of 

 the trunk, and the true dorsal contour is to be found se\"eral scale-rows 



6 Monogr. L^. S. C.coL Surv., VoL XI\', p. 56. 



