NEMATOGNATHI. 95 



ized Physoclistous Teliosts, yet all the subordinate characters disappear 

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

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

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

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

 Teleocefhali, 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 Fhysostomi Giiuther, v-viii.) 



A. Pnecoracoid arch present. 



B. Syinplectic bone none ; pterotic simple ; anterior vertebrae with ossicula audi- 

 tus ; supraoccipital and parietals co-ossified; maxillary imperfect, 

 forming the base of a barbel; no suboperculuiii.. NEMATOGNATHI, K. 

 BB. Symplectic bone present. 



C. Anterior vertebrae co-ossified and with ossicula auditns. 



PLECTOSPONDYLI, L. 

 CC. Anterior vertebrae similar, distinct, without ossicula auditus. 



ISOSPONDYLI, M. 



AA. Proecoracoid arch none. 



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

 and anterior vertebras simple ; parietals separated by supraoccipital. 



HAPLOMI, N. 



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

 symplectic; maxillary bone lost or connate ENCHELYCEPHALI, O. 



OEDEB K. NEMATOGNATHI. 



(The Cat-fishes.) 



Parietals and supraoccipital confluent. Four anterior vertebra co- 

 ossified, and with ossicula auditus. No mesopterygiuin. Basis crauii 

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

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

 backwards. One or two pairs of basal brauchihyals '; two pairs brauchi- 

 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 

 Physostoinous 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. Ainer. Phil. Soc. 1870, 452. 



