564 Mr. C. T. Reiran on (he 



Synopsis of the Genera. 



I. Prpecaudal vertebrae normal, with the ribs attached to simple para- 



pophyses and the neural arche3 without lateral processes ; end of 

 transverse process of fifth vertebra appearing as a rugose plate 

 behind the lateral cutaneous area. 



A. Head somewhat compressed and elevated ; tail and caudal ver- 



tebrae normal. 



1. Mesopterygoid smaller than metapterygoid ; pelvics behind the 



dorsal. 



GiV-membranes free from isthmus Xanyra. 



Gill-membraues attached to isthmus Gayatn. 



2. Mesopterygoid large, extending to hyomandibular above the 



reduced metapterygoid ; pelvics below the dorsal. 



B. Head depressed; tail long and slender; caudal vertebrae with 



laminar neural and haemal spines and lateral laminar processes 

 which may form external series of bony plates. 



Pelvics behind the dorsal Bi-eiteyisteinia. 



Pelvics below the dorsal Sisor. 



II. Anterior praecaudal vertebras with a series of processes on each side 



directed upwards and outwards from the bases of the neural 

 arches; head depressed, 



A. Lips normal ; mesopterygoid large, extending forward below the 



palatine and backwards to the hyomandibular ; complex cen- 

 trum rigidly united, but not ankylosed to cranium ; para- 

 pophysis of fourth vertebra a half-cylinder, of tifth a stuut 

 horizontal process ending just beneath the skin. 



1. Eibs inserted on normal transverse processes ; pelvics behind 



the dorsal; gill-membranes free or narrowly attached to 



isthmus. 



Thorax without longitudinal plaits Bayariiis. 



Thorax with longitudinal plaits ; palate toothed. . . . Eitclyptosternum. 

 Thorax with longitudinal plaits ; palate toothless . . Gh.iptostermim. 



2. Anterior ribs sessile, the rest on transverse processes which are 



forked at the base ; pelvics below the dorsal ; gill-membraues 

 broadly attached to isthmus Pseiidecheneis. 



B. Lips expanded and reflected ; mesopterygoid not reaching hyo- 



mandibular ; complex centrum ankylosed with cranium ; para- 

 pophyses of fourth and tifth vertebrae united to form a complete 

 cylinder on each side ; ribs on transverse processes which are 

 forked at the base ; gill-membraues broadly attached to isthmus. 

 Teeth all pointed ; gill-openings extending on to 



lower surface rarexostoma. 



Teeth all pointed ; gill-openings not extending on to 



lower surface Euchiloglnnis. 



An outer series of bluut compressed teeth Exostoma. 



