472 . WILLIAM K. GREGORY 



to be nearly related to the Scopelidas (p. 487), but are assigned 

 to the Isospondyli by Boulenger. They are represented in the 

 Upper Cretaceous of Europe and in the freshwater Eocene beds 

 of France and North America. The sole existing species is 

 known from the seas off Japan, South Africa, Australia, and New 

 Zealand. They are somewhat pike-like in form, with sturgeon- 

 like mouth and snout; they have scaly fins, peculiar ctenoid 

 scales of an advanced type, and a long 'accessory scale' on the 

 paired fins, like certain other members of this assemblage. 

 Resembling the Gonorhynchidse is the tiny fish Cromeria, recently 

 discovered in the White Nile, for which a new family has been 

 erected. 



Superorder Malacopteroidei (cont'd). 

 (Plate XXIX.) 



Order Ostariophysi 1 Sagemehl 1885. 



(Plectospondyli Cope + Glanencheli Cope + Nematognathi Gill.) 



In this principally fresh-water group, which comprises the 

 Catfishes, Carps, Characins and Gymnotids, the anterior four 

 vertebras are greatly modified, often coossifled, their ribs and 

 neural and hsemal elements forming a chain of bones connecting 

 the air bladder with the auditory organ. The importance of these 

 bones in classification was indicated by Cope in his diagnosis 

 of the orders Plectospondyli Cope (Carps and Characins) , Glan- 

 encheli Cope (Gymnotids), and Nematognathi Gill (Catfishes). 

 These ossicles have been shown by Sagemehl to be severally 

 homologous and to have the same relations with the spinal 

 nerves, throughout the order, which is hence regarded by Bou- 

 lenger as "one of the most natural groups of the class Pisces." 

 Points of agreement with the Isospondyli are: (1) the air 

 bladder, if well developed, communicates with the digestive tract 

 by a duct; (2) the pectoral arch is suspended from the skull; (3) 

 the mesocoracoid (precoracoid) arch is present; (4) the pelvic 

 fins if present are abdominal; (5) the fin rays are soft and articu- 

 lated, except the pectoral and the dorsal spines of catfishes, 



i odtdptov, a little bone, qivtios, bladder, in allusion to the Weberian 

 auditory ossicles. 



