DEVONIC FISHES OF THE NEW YORK FORMATIONS IO9 



extent as in Neoceratodus and Lepidosiren ; hence Cope's statement 

 requires rectification when it is said that the parasphenoid in modern forms 

 is abnormally produced behind.' The extreme thinness of the bone in its 

 anterior portion stands in decided contrast to the solidly ossified plate of 

 Ctenodipterines, and it is further noteworthy that no specimen has yet 

 enlightened us as to its relations with the palato-pterygoid cartilages. Near 

 the point of its greatest constriction, in what corresponds to the position of 

 the quadrate bone, is a well marked oval concavity, described by Cope as a 

 " glenoid fossa" ; and this may not improbably be looked upon as having 

 served for attachment of the mandibular suspensorium. Nothing whatever 

 is known of the characters of the latter, nor of the dentition ; and accord- 

 ingly these structures are inferred to have been cartilaginous. 



Reference has been made to the tubular sheath which inclosed the 

 notochord, and this we have stated to be supported below by the narrow pos- 

 terior projection of the parasphenoid, miscalled by Cope " descending axial 

 alae." The region traversed by the chordal sheath within the interior of 

 the head shield has been variously interpreted, Newberry having described 

 it as a " cerebral," and Cope as a " nuchal " chamber, both authors evidently 

 regarding it as completely closed on all sides. As a matter of fact, the 

 space designated by these writers as a "chamber" was closed at either end 

 by thin osseous partitions, and above by the cranial roof ; but it was clearly 

 open below on either side of the constricted portion of the parasphenoid. 

 We can not imagine this partially inclosed space to have been the seat of 

 any organ, although likely enough it contained fatty matter. Bearing in 

 mind these differences of interpretation, it may be profitable at this point 

 to examine Cope's account of the conditions observed by him in the holo- 

 type of the species, since unfortunately destroyed by fire. The following 

 extract occurs at page 452 of the article already quoted : 



Turning now to the inferior aspect of the skull, we observed, at the 



» ''The parasphenoid in both Lepidosiren and Ceratodus is produced abnormally, and 

 it is only necessary to imagine this part to be reduced to its normal length to have the 

 conditions found in Macropetalichthys." [Cope, E. D. On the Characters of some 

 Palaeozoic Fishes. U. S. Nat. Mus. Proc. 1891. 14:455] 



