Prof. E. D. Cope on the Systematic Relations of Fishes. 167 



pharyngeal much enlarged, articulating with cranium ; inferior 

 pharyngeals coossified. 24. Pharyngognathi (Burgall, Parrot- 

 fish). 



These orders will be more fully defined, and the families 

 which are referable to them pointed out. 



IV. General Observations. 



In tracing the affinities of the Physostomi, I have pointed 

 out the relation between the Chrondrostei and the Nemato- 

 gnathi, and between the Halecomorphi and thoi Isospondyli. 

 The first named of each of these pairs are the structural, and 

 probably genetic, predecessors of the second. The series com- 

 menced with the Catfishes may be continued into the Mormyri 

 and then to the families of the Plectospondyli, where the series 

 with altered vertebras and with ossicula auditus terminates. 

 The Characins, however, have considerable affinity to the 

 Isospondyli, especially in the type of their branchial bones. 

 From the latter group we pass to the Haplomi, and thence to 

 the Physoclyst groups. The eel-like groups form a special 

 line. The Glanencheli have cranial characters of the groups 

 with modified vertebrae, with fins of the more typical eels. 

 The latter show a steady approach in some points to the con- 

 ditions characterizing the Chondrostei. The loss of the maxil- 

 lary, of opercular bones, and of pharyngeal elements reminds " 

 one of these ; but in the loss of the premaxillary and great de- 

 velopment of the ethmoid, in the Colocephali, we have features 

 quite unique. The vertebral position of the scapular arch is 

 the only shark-character they possess ; while, on the other 

 hand, the Holostomi are undoubtedly related to the Masta- 

 cembelusj a real Physoclyst with spinous dorsal fin. These 

 relations are as yet entirely inexplicable. 



The affinities among the Physoclysti are more clear. Omit- 

 ting the genus just mentioned, we find the four orders with 

 ventral fins to form a true series, with a Synentognath varia- 

 tion, terminating in the greatly degraded order of Lopho- 

 branchii. The Percesoees give us our nearest connexion with 

 the groups with abdominal ventral fins, and lead at once to 

 the Percomorphi. From this centre radiate many lines of 

 affinity. One leads from the Chgetodontidas, through the Acro- 

 neuridae, to the Plectognathi, by the similarity in the ar- 

 rangement of the posttemporal and forms of the pharyngeal 

 apparatus. An important division of the Percomorphi has 

 the basis cranii simple and the branchials reduced above, viz. 

 the Scyphobranchii. The Cottidae are the most generalized 

 family of this group, and lead, on the one hand, to the Triglidas 

 of the Distegi, with which tliey are generally arranged, and. 



