88 NEW YORK STATE MUSEUM 



plate 3, figure 7, is labeled as having come from the top of Learn hill, in 

 the northern part of Ischua township, Cattaraugus county, and there are 

 others from near Portville and southeast of Olean, in the same State. 



Formation and locality. Chemung beds (Chautauquan) ; New York 

 and Pennsylvania. Catskill sandstone ; Tioga county, Pennsylvania. 



Subclass DIPNEUSTI 



Fishes with partially ossified skeleton, numerous membrane or dermal 

 bones, and persistent notochord ; skull autostylic ; dentition confined to 

 inner bones of the mouth ; gill clefts feebly separated, opening into a cavity 

 with membranous operculum ; paired fins archipterygial or reduced ; median 

 fins often subdivided ; exoskeleton consisting of true bony tissue ; sensory 

 canals well developed. 



The few existing Dipnoan ' species, comprised by the fresh-water 

 genera Neoceratodus, Protopterus and Lepidosiren, form a well nigh inap- 

 preciable remnant of a once flourishing and highly diversified race of lung 

 fishes, whose maximum development and specialization occurred during the 

 Devonic. One remarkable order comprising huge armored fishes passed 

 entirely out of existence during the lowermost Carbonic, without leav- 

 ing descendants. Such, at least, appears to be the most satisfactory inter- 

 pretation of the group now commonly known as Arthrodires. Another 

 order, that of Ctenodipterines, was conspicuous throughout the Paleozoic, 

 and attained a higher degree of specialization along certain lines than is 

 evinced by later forms. The geological history of the Sirenoid order, to 

 which Ceratodus and its modern descendants belong, is not traceable with 

 certainty earlier than the Triassic, although it is possible that some Paleo- 

 zoic remains, known chiefly by the dentition, properly belong here. That 

 primitive members of this order were in existence at least as early as the 



' As pointed out by Haeckel, Boulenger and others, the term Dipnoi, first applied by- 

 Johannes Miiller in 1845 fo^" the group of lung fishes, is improperly so used, having been 

 previously chosen by Leuckart as a name for Amphibians. There is no objection, however, 

 to retaining the name Dipnoan as a vernacular equivalent of Dipneusti, and it is here 



employed in that sense. 



