146 



SILTJRIDiE. 



longest, its length being one-fifth of the total. Pectoral spine ser- 

 rated along both edges, longer and stronger than that of the dorsal. 

 Ventral fin shorter than pectoral. All the fins black. 

 Guatemala. 



a. Twelve inches long. Guatemala. Purchased of Mr. Frank. 



b. Fine specimen, 13 inches long. Chiapan. From the Collection 



of Messrs. Godman and Salvin. 



12. Arius assimilis. 

 D. 1/7. A. 19. P. 1/10. 



The height of the body is contained four times and two-thirds in 

 tbe total length (without caudal), the. length of the head thrice and 

 three-fifths ; head much broader than high, its greatest width being 

 three-fourths of its length. Eyes rather small, situated nearer to the 

 end of the snout than to that of the operculum; the length of the snout 

 is three-fifths of the width of the interorbital space. The median longi- 

 tudinal fonticulus on the upper side of the head does not extend to the 

 base of the occipital process. Teeth on the vomer 

 but slightly separated in the middle, forming a 

 pair of oblong transverse patches which are 

 confluent with those on the palatine bones ; the 

 latter are short, club-shaped. The band of 

 intermaxillary teeth is five times as broad as 

 long. All the teeth villiform. The maxillary 

 barbels extend nearly to the end of the head ; the length of the outer 

 ones of the mandible is one-half or two-thirds of that of the head. 

 Crown of the head granular, the granulations being arranged in 

 radiating streaks. Occipital process broader than long, triangular, 

 with its hinder end concave. The basal bone of the dorsal spine of 

 moderate size, crescent-shaped. Dorsal spine of moderate strength, 

 more than half as long as the head, granulated in front and slightly 

 serrated behind ; the first soft ray is longer than the spine and as 

 high as the body. Adipose fin shorter than the dorsal. Caudal 

 deeply forked, with the upper lobe longest, its length being contained 

 five times and a half in the total. Pectoral spine serrated along its 

 inner edge and on the extremity of the outer edge. Ventral fin 

 shorter than pectoral. Sides of the body silvery ; vertical fins grey- 

 ish ; basal half of the inner side of the paired fins black. 



Guatemala. 

 a. Fine specimen, 13 inches long. Lake of Yzabal. From the Col- 

 lection of Messrs. Godman and Salvin. 



. Hexanematichthys hymenorrhinos, Bleek. Versl. & Mededeel. Akad. 

 Wetensch. Amsterd. 1862, xiv. p. 377, appears to be closely allied 

 to the above species, and we should not hesitate to refer our speci- 

 mens to it if the barbels of Bleeker's species were not much longer, 

 those of the maxillaries extending or to the base of the ventral fin, 

 and the outer ones of the mandible to the base of the pectoral. The 

 specimen in the Leyden Museum is 8^ inches long. 



