154 SILURIDiE. 



of the dorsal spine ; this plate is separated from the occiput by a 

 transverse groove ; it is subquadrangular and nearly as broad as 

 long. The height of the body is one-fifth of the total length (with- 

 out caudal), the length of the head two-sevenths. The upper jaw 

 projects much beyond the lower. Teeth on the palate in two widely 

 separate triangular patches. The maxillary barbel extends to the 

 prseopercular margin. Pectoral spine very strong, as long as, but 

 stronger than, that of the dorsal. Adipose fin longer than the dorsal. 

 (Val.) 



South America. 



Valenciennes briefly mentions two other species which appear to 

 agree with A. grandicassis in having a large dorsal plate behind the 

 occiput ; but as they are said to have only six dorsal rays, we dare 

 not refer them to this genus : — 



a. Arius strict icassis, Cuv. & Val. xv. p. 58. D. 1/6. A. 18. P. 1/12. 

 Dorsal plate thrice as long as broad ; barbels short. — Cayenne. 



b. Arius parmocassis, Cuv. & Val. xv. p. 57. D. 1/6. A. 15. P. 12. 

 Dorsal plate ovate, narrower in front than behind ; the palatine 

 teeth form two large patches, the anterior and interior angles of 

 which are produced inwards, without touching each other. Barbels 

 rather short. — Bahia. 



There is evident confusion in Valenciennes's account of these two 

 fishes ; he commences the description of his second species (A. parmo- 

 cassis) by comparing it with two preceding species ; and the formula 

 of the fins also is given in an unusual form. 



Bagrus valenciennei, Casteln. Anim. Amer. Sud, Poiss. p. 31. pi. 13. 

 fig. 1 , appears to belong to this group of Siluroids, and is possibly 

 identical with A. parmocassis, or with Bagrus albicans (see p. 150). 



b. No large interneural shield on the nape. 

 a. African species. 



28. Arius heudelotii. 

 Arius heudelotii, Cuv. fy Val. xv. p. 73. pi. 428. 

 D. 8. A. 16. P. 10. 

 The length of the head is one-third of the total (without caudal) . 

 Crown of the head granulated. The maxillary barbel extends beyond 

 the operculum. Basal bone of the dorsal spine small ; dorsal and 

 pectoral spines strong -and very long, serrated along both edges. 

 Adipose fin very short. The upper caudal lobe is the longer, one- 

 sixth of the total length. The teeth on the palate are villiform, and 

 form two small, widely separate patches. ( Val.) 

 Senegal. 



29 Arius parkii. 

 D. 1/7. A. 20. P. 1/10. 

 The height of the body is contained five times and a half in the 



