HETEROTIS. 149 



thin skin confluent with the bones ; body covered with large bony scales, 

 composed of pieces like mosaic. No oviducts. 



Fresh waters of South America, Australia, the Malay Archipelago, 

 and Africa. 



1. HETEROTIS. 

 Sudis (non Rafin.), part., Cuv. Regne Anira. i. p. 180 (1817). 

 Heterotis (Ehrenb.), Cuv. & Val. Hist. Poiss. xix. p. 465 (1846) ; Giinth. Cat. 



Fish. vii. p. 380 (1868) ; Bouleng. Fish. Nile, p. 83 (1907). 

 Helkohranclius, Hyrtl, Denkschr. Ak. Wien, viii. 1854, p. 86. 



Mouth moderate, with small conical teeth forming a single series in 

 the praemaxillaries, maxillaries, and dentaries ; groups of villiform teeth 

 on the entopterygoids and on the tongue. Branchiostegal rays 7 or 8. 

 Body strongly compressed. Dorsal and anal fins equally developed, on 

 the caudal region of the body, elongate and narrowly separated from the 

 small caudal ; ventral fi.ns nearer end of snout than caudal fin, with 

 6 rays. Vertebrae 27-1-42-43. Air-bladder cellular, lodged in the 

 closed haemal arches of the caudal vertebrae. Fourth branchial arch 

 with an accessory breathing-organ. 



A single species. 



1. HETEROTIS NILOTICUS. 

 Sudis nilotims (Ehrenb.), Cuv. Rfegne Anim. 2nd ed. i. p. 328 (1829) ; Rlipp. 



Beschr. n. Fische Nil, p. 10, pi. iii. fig. 2 (1829). 

 Sudis adansonii, Cuv. 1. c. 



Garafche, Rifaud, Voy. Egypte, pi. cxc. (1830). 

 Heterotis ehrenbergii, Cuv. & Val. Hist. Poiss. xix. p. 469, pis. ccccclxxxiii. & 



ccccclxxxiv. (1846) ; Hyrtl, Denkschr. Ak. Wien, viii. 1854, p. 73, pis. i.-iii. 

 Heterotis adansonii, Cuv. & Val. t. c. p. 478. 

 Heterotis nilotims, Giinth. Cat. Fish. vii. p. 380 (1868), and Petherick's Trav. ii. 



p. 266 (1869) ; Steind. Sitzb. Ak. Wien, ixi. i. 1870, p. 565, pi. viii. fig. 2 ; 



Hempr. & Ehrenb. Symb. Phys., Zool. pi. i., and Zoot. pis. viii. & ix. (1899) ; 



Budgett, Tr. Zool. Soc. xvi. 1901, p. 128, pi. xi. figs. 6 & 7 ; Bouleng. Fish. 



Nile, p. 84, pi. xiv. (1907). 

 Depth of body 3^ to 4| times in total length, length of head 

 3J to 4| times. Head short and thick, convex above, its upper surface 

 and sides rugose, granulate in the adult, with large sensory pits ; snout 

 short, rounded, 3f to 5 times in length of head ; eye perfectly lateral, 

 its diameter 5J to 8 times in length of head and 2 to ol times in 

 interorbital width; mouth with thick lips, straight and transverse in 



