114 



TRANSACTIONS OF THE AMERICAN PHILOSOPHICAL SOCIETY 



(suborbitals); — the ventral one, or some of them, can probably, as we have seen, be con- 

 sidered as corresponding to the quadratojugal; in the Teleosts the homologues of the 

 squamosal elements usually seem to be reduced. Sometimes, however, it is possible that 

 parts of them may persist in the plates of the infraorbital chain, in the cases when these 

 plates are much developed and cover the cheek between the orbit and the preopercular 

 to any great extent." 



The subopercular of the Paljeoniscldae was at first identified by Traquair (1877, p. 20) 

 as the interopercular, on account of the presence in Rhabdolepis and Cosmoptychius of a 

 small additional plate below the opercular; but in the later parts of the same monograph 

 (e.g. 1907, p. 94; 1909, p. 122) he labeled this element subopercular, which is the identifica- 

 tion adopted by Watson. 



The palate of Elonichthys and related genera, as described by Watson (1925, 1928), 

 closely resembles that of the primitive Crossopterygii in all important features. The 

 fixed premaxillse and maxillae formed the margin for a row of tooth-bearing plates borne 

 by the primary upper jaw, which included ossifications named suprapterygoids (2-5), 

 metapterygoids, palatine (= anterior suprapterygoid), pterygoids (= meso- or internal 

 pterygoids of teleosts), ectopterygoids (= so-called pterygoids of teleosts). 



The basipterygoid processes of the parasphenoid were immediately behind the orbits 

 on the anterior half of the skull and the parasphenoid, unlike that of later ganoids and 

 teleosts, did not extend back beneath the occiput (Watson, 1925). 



The mandible of Elonichthys and its allies, as described by Watson, included an entire 



orbif 



B p^^ 



facpf for hyom 



orbit' 



facetforkyom 



tfzj's^^ 



Fig. 13. Neurocranium of (A) modern shark, Chlamydoselachus (after Allis) compared with (B) that of Carboniferous 

 palaeoniscid (after Watson). 



Note the relatively enormous orbit and very small olfactory capsule in (B). 



