550 " ^- l'OI'I ARD, 



5) The resemblance of Chaetostomus to Clarias and Aitchenaspis 

 is important, because 



a) The African and South American faunas are widely se[)arate ; 



b) Chaetostomus in its dermal skeleton is most archaic. 

 Clarias is thus shown to have a very ancient type of lateral line 



system. 



()) Comparison of the mucous canals of Clarias and Coccosteus, as 

 far as can be discovered from Pander's figures supports Prof. Huxley's 

 view that the Placodermi and Siluroids have a genetic relationship. 



7) Taking (6) as true Coccosteus forms in the relations of the 

 infraorbital and opercular canals a link with the Selachii. A parallel 

 case is seen in the transition from Polypterus through the fossil 

 Crossopterygidae to Chlamydoselaclius. 



8) One important feature, the presence of a canal, may be con- 

 fined to the Rays and Siluroids. 



March 1892. 



Literature. 



Allis, Lateral line system in Amia Calva, in : Journal of Morphology, 



vol. 2, April 1889 (with literature). 

 Bodenstein, Seitencanal von Cottus gobio, in: Zeitschr. f. wiss. Zool., 



Bd. 37, 1882. 

 Gabman, Lateral canal system of the Selachia and Holocephala, in : 



Bull. Mus. Comp. Zool. Harvard, vol. 17, 1888. 

 GuiTEL, Recherches sur les Lépadogasters, in : Arch, de Zool. Exp. et 



Gén. (sér. 2), T. 6. 

 Huxley , Preliminary essay upon the systematic arrangement of the 



fishes of the Devonian epoch, in: Mem. Geol. Survey United Kingdom, 



1861, Dec. 10. 

 Pander, Ueber die Placodermen des devonischen Systems, St. Petersburg 



1857. 

 Sagemehl, Das Cranium der Chai'aciniden, in: Morph. Jahrb., Bd. 10, 



1884. 



