59. ARITTS. 153 



Crown of the head granular, the granulations being arranged in 

 radiating streaks. Occipital process subsemicircular, broader than 

 long ; the basal bone of the first dorsal spine is very large, larger 

 than the occipital process, subquadrangular, rather broader than long. 

 Dorsal spine of moderate strength, as long as the head without snout, 

 granulated in front, and scarcely serrated behind ; the first soft ray 

 rather longer than the spine, as high as the body. Adipose fin 

 longer than the dorsal. Caudal deeply forked, with the upper lobe 

 longest, its length being a little more than one-sixth of the total. Pec- 

 toral spine serrated along both edges, longer and stronger than that 

 of the dorsal. Ventral fin shorter than pectoral. Coloration uniform. 



Brazil; Surinam. 

 a. Fine specimen, 16 inches long. South America. 

 b~c. Adult. Surinam. From the Stuttgart Museum. 



d. Young, 8 inches long. Brazils. Presented by Lord Stuart. — This 



specimen differs a little from the larger one, the differences 



being due probably to age. The patch of vomerine teeth is 



smaller and narrower ; the bands of 



palatine teeth are more separated from 



each other by a free space in the'middle. 



The basal bone of the dorsal spine is 



somewhat shorter, or broader. In other 



respects the specimens are perfectly 



alike. 



e. Young. Old Collection. 



26. Arius parkeri. 

 Siluras parkeri, Traill, Mem. Went. Soc. 1832, vi. p. 377. pi. 6. fig. 1. 

 Arius quadriscutis, Cuv. §Val. xv, p. Ill; Kner, Sitzgsber. Wien.Acad. 

 1858, xxvi. p. 389. 



D. 1/7. A. 19. P. 1/11. Vert. 18/31. 



Occipital process twice as broad as long ; a large subquadrangular 

 nuchal plate, emarginate anteriorly and posteriorly. The maxillary 

 barbel extends to the middle of the opercle. The teeth on the palate 

 are granular, and form two large ovate patches, which touch each 

 other in their whole length. Dorsal spiue slightly serrated ; adipose 

 fin nearly as long as the anal. ( Vol.) 



Cayenne; Surinam. 



II. Teeth on the palate in two generally widely separate patches ; some- 

 times the vomerine teeth are present, but widely separate into two 

 small groups which may be continuous with the palatine teeth. 



A. Teeth on the palate villiform. 



a. A large intemeural shield on the nape. 



27. Arius grandicassis. 



Arius grandicassis, Cuv. fy Vol. xv. p. 54. pi. 427. 

 D. 1/7. A. 18. P. 1/12. 

 A very large bony plate between the occiput and the basal bone 



