76 Mr. C. T. Regan on the 



Teleostomi, viz. Cliondrostei, Teleostei, Crossopterygii, and 

 Dipneusti, I now regard as sub-classes of the class Pisces. 

 These four sub-classes may be arranged in two series : in the 

 Actinopterygian series (Cliondrostei and Teleostei) the duct 

 of the air-bladder opens dorsally or dorso-laterally into the 

 alimentary canal, the branchiostegals retain their primitive 

 serial arrangement, and the supports of the paired fins are 

 either in tiie form of a series of parallel pterygiopiiores each 

 of which is segmented into a basal and a radial portion or are 

 modified from this plan by a sim]jle process of concentration 

 and reduction ; in the Crossopterygian series (Crossopterygii 

 and Dipneusti) the opening of the pneumatic duct is ventral, 

 the branchiostegals are replaced by a pair of gular plates, 

 and the paired fins are more or less lobate, with their 

 supports tending to the biserial arrangement with axial 

 basalia. 



The Teleostei are well marked off from the Chondrostei 

 by the absence of clavicles and of pelvic radials, the reduction 

 in number of the dorsal and anal fin-rays, so that each has 

 its own pterygiophore, and the shortening of tlie upturned 

 axis of the caudal fin, which is homocercal or abbreviate 

 heterocercal. Thus defined they include the Holostei, a 

 group which cannot, in my opinion, be maintained. 



The ordinal names are not formed on any definite plan, but 

 usually have some reference to the peculiarities of tlie group ; 

 it seems to me useful always to form subordinal names 

 with the termination -videi, and when families are arranged in 

 divisions or superfaiuilies to give these groups names ending 

 in -formes. 



Synopsis of the Orders and Sub-orders of the 

 Sub-class Teleostei. 

 I. Spleuial well developed. 



A. Vertebral centra incomplete, or with alternating pleuro- and 

 hypo-centra in the caudal region . . 1. Protoqioiulyli. 



1. Prfemaxillaries meeting in the middle line ; caudal hu supported 



bj' little expanded hiemal spines. 



No endochondral supraoccipital ; parietals 

 united by suture ; opercular bones com- 

 plete 1 «. Amioidei. 



An endochondral supraoccipital ; parietals 

 united by suture ; opercular bones com- 

 plete 16. Dapediodei. 



No endochondral supraoccipital : parietals 

 separated by a median dermal bone ; sub- 

 and iuter-opercukim absent I c. Pyenodontoidei, 



2. Prjemaxillaries separated by an etlimo-vomerine rostrum ; lowf^r 



lobe of caudal tin supported by a sin^-'le much expanded 

 htemal spine Id. I'achycurmoidei 



