40 



BKITISH FOSSILS. 



Miller, Giebel, and Pander have agreed upon the propriety of 

 separating Cheirolepis from the other Acanthodidse of Agassiz, 

 and Pander proposed to form for it a distinct family, that of the 

 Cheirolepini. Granting, as I think every one must do, the 

 justice of this step, the question next arises in what suborder of the 

 Ganoids does this family arrange itself 



It certainly is not one of the Crossopterygidse, for it has but a 

 single, comparatively short, dorsal fin, neither pectorals nor ventrals 

 are lobate, and there are no jugular plates ; still less can Cheirolepis 

 be ranked among the Amiadse or Chondrosteidae. On the other 

 hand, it presents certain points of resemblance with Paleoniscus, 

 and through those forms connects itself with that large bod}^ of 

 fossil fishes which have more or less direct relations with 

 Lepidosteus. Perhaps then, Cheirolepis ought to be regarded as 

 the earliest known form of the great suborder of the Lepidosteidse. 



In the absence of a full knowledge of the head, of the paired fins 

 and of the dentition, it would be hazardous to form any decided 

 opinion as to the affinities of Tristichopterus ; I strongly suspect, 

 however, that it will turn out to be the type of a new family allied 

 to the Ctenododipterini and C oelacanthini. 



The cranio-facial bones are lettered as follows in the woodcuts : — 



S. O. Supra-occipital. 

 Fr. Erontal. 

 Eth. Ethmoid. 

 Ep. Epiotic. 

 Pa. Parietal. 

 Sq. Squamosal. 

 Ft. F. Post-frontal. 

 Pr. F. Pre-frontal. 

 S. T. Supra-temporal. 

 Ft. O. Post-orbital. 

 Sb. O. Sub-orbital. 



Mx. Maxilla. 



Frmx. Premaxilla. 



H. M. Hyomandibular bone. 



Qu. Os quadratum. 



S. S. Supra-scapular. 



Op. Operculum. 



S. Op. Sub-operculum. 



Ju. Jugular bones. 



Sp. O. Spiracular ossicles. 



St. O. Supra-temporal ossicles. 



P.O. " Pre-operculum " occurs in the woodcut, fig. 2 ; but I am now much inclined 

 to doubt the existence of a true pre-operculum in any Crossopterygian fish. 



T. H. Huxley. 



Jermyn Street, Nov. 1, 1861. 



[Note. — By the great kindness of Dr. Taylor of Elgin, I have just had the opportunity 

 of exan)ining a beautiful, almost entire, specimen of Ghjptopomiis, with two dorsal, and 

 exquisitely lobate pectoral, fins. — T. H. H., Nov. 18th,] 



