VERTEBRATE ZOOLOGY. 497 



ica; and (3) the not-long-ago discovered JVeoceratodus, of 

 Australia. The type is quite exceptional now, and stands 

 out thoroughly isolated from the fishes of the present, and, 

 in fact, cenozoic ages, and is, to some extent, intermediate 

 between the typical fishes and amphibians. It is, however, 

 yearly becoming more and more evident that in the early 

 mesozoic, as well as later palaeozoic times, it was a predomi- 

 nant type of fishes, and that this type was widely distrib- 

 uted in the sea as well as in fresh water, and was manifested 

 under numerous and diverse forms representing a number of 

 distinct families and higher groups. During the past year 

 our knowledge of the order has been extended by the inves- 

 tigations of Professor Traquair, of Edinburgh, and Professor 

 Newberry, of New York. The former has especially eluci- 

 dated the affinities of the common Devonian genus Dipterus, 

 and the problematical forms indicated under the names Pa- 

 Icedcqjhus, Holodus, Heliodus, Conchodus, and Cheirodus. The 

 main facts brought out are: (1) that Dipterus agrees with 

 Ceratodus in being "autostylic" and not "hyostylic," as has 

 been suggested ; (2) that Palcedaphus, Holodus, and Helio- 

 dus, were based on remains of the same genus, and that that 

 genus was a gigantic Dipnooan ; and (3) that Cheirodus of 

 McCoy, Avas intended for the Platysomid genus named Am- 

 phicentrum, in 1836, by Young, but that Cheirodus of Pan- 

 der is probably identical with Conchodus, and belongs to 

 the Dipnoi. The huge Dinichthys of the Ohio carboniferous 

 lias also been referred to the Dipnoi by Newberry. The ref- 

 erence of these forms to the Dipnoi involves that of a num- 

 ber of others. Some of these had, indeed, already been ap- 

 proximated to the type in question, but the want of definite 

 knowledge regarding some essential points of structure ren- 

 dered such approximations provisional ; the position of the 

 genera referred to may now be regarded as tolerably assured. 



Ceratodus in the American Jurassic. 



The family of Ceratodontids, so interesting from several 

 points of view, and to which attention has been called in pre- 

 vious volumes of this Annual, has now been found to have 

 flourished in the American waters of the Jurassic age. A 

 left lower dental plate has been discovered with other verte- 

 brate remains in the Jurassic of Colorado, and on it has been 



