CLASS TFIOATION OF DEVONIAN FISHES. S3 



behind the body armour, and were perliaps connected with ventral 

 fins ; but I enter into no particular description of these, as they 

 are not essential to my present purpose. 



For some years past I had suspected that the modern Siluroids 

 presented more analogies to the seemingly aberrant Devonian fishes 

 than any other members of the class Pisces, and from the examina- 

 tion of dried specimens, I had even pitched upon the Siluroid genus 

 Clarias as that most likely to help me to understand Coccosteus ; 

 but it was not until my friend and former pupil, Mr. J. J. Monteiro, 

 brought home for me from Congo some specimens of Clarias 

 capensis preserved in spirits, that I was able to examine the 

 osseous structure of that fish with sufficient care and thoroughness 

 for the purposes of an efficient comparison. 



In fig. 20 a careful, reduced representation of the top of the skull 

 of this fish is given, and it will be seen, that in everything but the 

 minor details of form, it agrees with Coccosteus. The middle line of 

 the skull is, as in the latter genus, occupied by three bones. S.O., 

 the supra-occipital, is, in the recent form, pointed behind ; Fr., the 

 principal frontal, is, as in the fossil, four-rayed ; it exhibits a 

 considerable gap or fontanelle, but no median suture ; Eth., the 

 ethmoid, and Pmx., the premaxilla, correspond exactly in the two 

 skulls, if we leave out of consideration the position of the suture 

 seen in the fossil in this region. The bone Pr. F., which can be 

 at once identified as the prefrontal in Claria.s, and which sends 

 down a process dividing the orbit from the nostril, obviously 

 corresponds with the similarly related bone in Coccosteus ; while 

 in Clarias the orbit is completed below by the spatulate suborbital 

 bone, Sb. O., smaller in proportion and undivided, but otherwise 

 similar to the bone z, z' of Coccosteus. The post-orbital bone, 

 Pt. 0., and the supra-temporal bone, S. T., of the former appear to 

 have their homologues in the bones x and y of the latter fish. 



The space between the frontal, the supra-occipital, and the supra- 

 temporal is occupied, in Clarias, by two bones, the anterior of 

 which certainly represents the post-frontal ; while the posterior 

 occupies the situation of no less than three distinct bones in the 

 lieads of ordinary fishes, viz., the parietal, the squamosal, and the 

 epiotic. The reduction in the normal number of bones which 

 obtains in the Siluroid has been carried a step further in Coccosteus, 

 where the plate lettered for shortness' sake only Pa. Ep. is the only 

 representative of the bones Pt. F. and Pa. Sq. Ep. of Clarias. 



Lastly, comes the bone S.s. naturally united in Clarices to Pa. 

 Sq. Ep. and to S. T., and which corresponds with the supra-scapula 



10 c 2 



