2/3 



or conical in one, two or three groups on each side. Gill- 

 membranes united, connected with the isthmus but with a 

 free posterior margin. 5 9 branchiostegals. 



Fig. 1 06. Arius thalassinus (RUpp.). 



Synopsis of the species. 



I. Teeth on the palate granular. 



A. Teeth in four groups (the anterior groups some- 

 times rudimentary). (Ariodes Blkr.). 



1. posterior patches in a broad oval, conver- 

 ging behind. 



a. anterior patches well developed, sides of 



occipital process convex A. crossocheilus p. 276. 



b. anterior patches rudimentary or nearly 

 wanting, sides of occipital process straight. 



a. head 3 times in length A. macrocephalus p. 277. 



/3. head more than 3 times in length. . A. argyropleuron p. 278. 



2. posterior patches in a narrow oval, parallel 

 or diverging behind. 



a. parallel, occipital process with irregular 

 convex sideborders, its hinderhalf trian- 

 gular A. polystaphylodon p. 280. 



b. diverging behind. 



K. occipital process oval A. leiotetocephalns p. 282. 



INDO- AUSTRALIAN FISHES II. 18 



