NEMATOGNATHI. 95 



ized Physoclistous Teliosts, yet all the subordinate characters disappear 

 as we approach the poiut of union of the two groups, leaving only the 

 presence of the air-duct as the ultimate distinctive character of the 

 Physontomi. In view of this inosculation of the two groups, many 

 writers (following Professor Gill) have united them both into one order, 

 Tcleoccphali, after the exclusion of various aberrant members of each. 

 The retention, in some form, of groups emphasizing the difference be- 

 tween the spinous and the soft-rayed fishes seems to us very convenient. 



(Order rhijsoxtomi Guntlier, v-viii.) 



ANALYSIS OF ORDERS OF PHYSOSTOMI. * 



A. Pr^coracoid arch present. 



B. Symplectic bone none ; pterotic simple ; anterior vertebra) with ossicvila audi- 

 tus ; 8upraoccii)ital and parietals co-ossified ; maxillary imperfect, 

 forming the base of a barbel; no suboperculum.-NEMAXOGXATHi, K. 

 BB. Symplectic bone present. 



C. Anterior vertebriB co-ossified and with ossicula auditus. 



Plectospoxdyli, L. 

 CC. Anterior vertebra) similar, distinct, without ossicula auditus. 



ISOSPONDYLI, M. 



AA. Praecoracoid arch none. 



D. Scapular arch suspended to cranium ; a symiilectic bone ; pterotic 

 and anterior vertebra) simple ; parietals separated by supraoccipital. 



Haplomi, N. 



DD. Scapular arch free behind the cranium; parietals in contact; no 



symplectic; maxillary bone lost or connate Exchelycephali, O. 



Order K -NEMATOGNATHI. 



{The Cat-fislies.) 



Parietals and supraoccipital confluent. Four anterior vertebra co- 

 ossified, and with ossicula auditus. No mesopterygium. Basis cranii 

 and pterotic bone simple ; no coronoid bone. Third superior pharyn- 

 geal bone wanting, or small and resting on tlie fourth ; second directed 

 backwards. One or two pairs of basal branchihyals ; two pairs branchi- 

 hyals. Suboperculum wanting. Premaxillary forming mouth border 

 above. Interclavicles present. No scales. Skin naked or with bony 

 plates. 



" This division is the nearest ally to the sturgeons {Chondrostei) among 

 Physostomous fishes, and I imagine that future discoveries will prove 

 that it has been derived from that division by descent. In the same 



• After Cope, Trans. Amer. Phil. Soc. 1870, 452. 



