3. PLOTOSTTS. 23 



5. Heterobranchus isopterus. 



Heterobranchus isopterus, Meek. Poiss. Cute de GuinSe, p. 108. tab. 22. 

 macronema, Bleek. I. c. p. 109. tab. 21. fig. 1, tab. 22. fig. 2. 



B. 9. D. 31-32. A. 41-45. P. 1/10. 



Adipose fin rather shorter and lower than the rayed dorsal, com- 

 mencing at a short distance behind it, and terminating immediately 

 before the caudal ; pectoral spine scarcely serrated. The length of 

 the anal fin is considerably more than one-third of the total (without 

 caudal). The nasal barbels extend to the end of the head, and those 

 of the maxillaries to or beyond the extremity of the pectoral fin. 

 The vomerine teeth form an arched narrow band, narrower than 

 that of the intermaxillaries. Black above and on the sides ; the 

 caudal and anal fins with a narrow whitish margin. 



West Africa. 



a-b. Seven inches long. West Africa. From the Collection of C. 

 Swanzz, Esq. 



6. Heterobranchus laticeps. 



Peters, Monatsber. Acad. Wiss. Berl. 1852, p. 682. 



B. 9-10. D. 30-33. A. 44-45. P. 1/11-12. 

 The adipose fin commences at some distance behind the dorsal, 

 and is continued over and beyond the root of the caudal. The 

 maxillary barbels reach beyond the ventral fins. Anal and caudal 

 fins with red margins. {Pet.) 

 Coast of Mozambique. 



Hyrtl (Denkschr. Acad. Wiss. Wien, 1859, xvi. p, 17) mentions a 

 skeleton in his collection under the name of H. laticeps ; it has 18 

 abdominal and 39 caudal vertebras. 



Second Group. PL0T0SINA. 



The gill-membranes are not confluent with the skin of the isth- 

 mus, or united with it by a narrow strip only, remaining more or 

 less separate. The dorsal is divided into two portions : a short 

 anterior with a strong spine, and a long posterior which, like 

 the anal, is confluent with the caudal. Ventrals many-rayed. 



Coasts of the Indian Ocean and Archipelago ; Western Polynesia 

 and Australia. 



3. PL0T0SUS. 



Plotosus, Lacep. v. p. 129. 



Plotosus, sp., Cuv. $■ Val. xv. p. 410 ; Kner, Sitzgsber. Wien. Acad. 

 1855, xvii. p. 151. 



A short dorsal in front, with a pungent spine ; a second long dor- 

 sal is united with the caudal and anal into one fin, which is pointed 

 behind. Teeth in the upper jaw conical, on the vomer molar-like, 



