Cope. ] 60 [May 20, 
possess the basilar interneural bones, which as I have pointed out,* only 
exist in the Physoclysti in small development in the Batrachide; and 
occur in various degrees of development in some Physostomi, being 
especially elongate in the anal fin of Ama. It is even possible that another 
element enters into the series connecting the neural spines with the dorsal 
fin-rays. The pectoral fin possesses fourteen or fifteen basilar radial bones ; 
a character which like the last, is not found in the Plectognathi; these 
fishes having but three or four such elements. These two points indicate 
a lower position than that of the latter order, and a relation to it similar to 
that which Amu bears to the Jsospondyli. It goes to show that even 
among some of the earlier fishes, physoclystous characters were fore- 
shadowed. I therefore establish a new order for its reception to take its 
place at the base of the line of Physoclysti. 
As a résumé of the preceding inquiry, the following table of the families 
treated of, with their definitions, is now given : 
Order ISOSPONDYLI. 
Physostomous fishes with distinct parietal bones; unmodified anterior 
vertebre ; and three or four basilar bones of the pectoral fin. Symplectic 
and preecoracoid bones present so far as known. 
Fam. Sauropstpai (Sauroides Agass. partim. ) 
Teeth of different sizes, the large raptorial ones mingled with small ones ; 
vertebral column osseous ; no basilar interneurals or interheemals. 
1. Caudal fin with many vertebre ; scales rhomboid ;—Pygopterus, Hugna- 
thus. 
2. Caudal fin with few vertebre ; scales rhomboid ;—Pachycormus,+ 
Sauropsis, Macrosemius, Belonostomus, Aspidorhynchus. 
3. Caudal fin with numerous vertebre ; scales rounded ;—Megalurus, Cal- 
lopterus, + Attakeopsis. t 
4. Caudal fin with few vertebre (in some instances apparently none); 
scales rounded ;—Caturus, Leptolepis, Anedopogon,S Thrissops. 
Fam. Leprporipa, (Lepidoides Agass. partim.) 
Teeth simple, often obtuse, in one or many rows, without elongate ones 
intermixed; no basilar interneurals or interhemals; vertebree with the 
centra incompletely ossified ; | (scales rhomboid ; caudal fin vertebrated. ) 
Amblypterus, Palwoniscus, Eurynotus, Semionotus, Lepidotus, Pholido- 
phorus, Microps, Notagogus, Ophiopsis, Cosmolepis, Plenropholis. 
Fam. Dapepipa mihi. 
Teeth uniform, obtuse ; vertebree with incompletely ossified centra ; || the 
interneural spines commencing at the head; a complete series of basilar 
interneural and interhzemal spines ;| Platysomus, Dapedius, Tetragonolepis. 
* Transac. Amer. Philos, Soc. 1871, XIV, p. 451. 
+ Vide P. heterurus and P. macropterus Ag. 
{ Thiolliere et Gervais Poissons Foss. de Bugey. 
7 Cope, Proceedings American Philosophical Society, 1871, p. 53. 
| These statements are derived from Agassiz, Poissons Fossiles. 
q Agass. Poiss. Fossiles, II. Pl. D. fig. 2. 
