CATALOGUE OF THE FISHES OF NORTH AMERICA. 



Class L— LEPTOCARDII. (I) 



Order A.— CIRROSTOMI. (A) 



Family I.— BEANCHIOSTOMID^. (1) 



1.— BRANCHIOSTOMA Costa. (1) 



1. BranchioBtoma lanceolatum Pallas. E. S. C. P. (1) 



Class II.— MARSIPOBRANCHII. (II) 



Order B.— HYPEROTRETA (B) 



Family IL— MYXINID^. (2) 



2.— MYXINE Linnjeus. (2) 



2. Myzine glutinosa LinnsBus. B. Eu. (2) 



Family III.— BDELLOSTOMID^. 

 3.— POLISTOTREMA Gill. (3) 



3. Polistotrema dombeyi Miiller. C. (3) 



Order C— HYPEROTRETA. (C) 



Family IV.— PETEOMYZONTID^. (3) 



4.— AMMOCCBTES Dum6ril.' (3&.)(4,5) 



§ Entosphenua Gill. (3&.) (4, 5, 6) 



4. Ammocoetes trideutatus Gairdner. C. Ana. (4) 



1 For discussions of the genera of PetromyzontidcB see Gill (Proc. U. S. Nat. Mus., 

 1882, 552) and Jordan & Gilbert {ibid., 1883, 208). Our species fall most naturally into 

 two groups, which we may call genera. Ammocoetes with the discal and peripheral 

 teeth differentiated, and the supraoral lamina (maxillary tooth) crescentiform, and 

 Petromyzon having the discal and peripheral teeth in obliquely decurved continuous 

 rows, and the supraoral lamina contracted, with 2 or 3 converging teeth. In both 

 groups are minor modifications, indicative of subgenera, the marine species of each 

 {marinus, tridentatm) being stronger, with more specialized dentition than the small 

 fluviatile forms. 



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