AEIUS. 127 



e5-e 6. Fontanel produced into a feeble groove wHch nearly reaches the parieto-occipital ; occipital 

 process keeled, sub triangular, about as broad as long, with sides slightly concave and apex more or less 

 emarginate ; dorsal shield small, siibcreseeiitio. Width of mouth i the width of head ; prajmaxillary 

 band of teeth 3i to 4 times as long as broad ; teeth on the palate obtusely conical, in 2 rather small 

 well-separated subovate patches ; maxillary barbel extending to basal part of pectoral. 11 gill-rakers 

 on the lower part of the anterior arch. Dorsal I 7 ; spine f the length of head ; adipose fin shorter than 

 the dorsal. Anal 19-21. Pectoral spine f the length of head, with the inner edge very strongly 

 serrated. Inner surface of the paired fins blackish. 



Hah. Mexico, Eio Papaloapam ^ ; Guatemala, Rio Motagua ^ (Scdvin). 



Here described from the types of the species, three specimens measuring from 180 

 to 200 mm, in total length. 



This is the only member of the genus known from the Atlantic slope of Mexico and 

 Central America. 



2. Arius liropus. 



Tachysurus liropus (Bristol), Jord. & Everm. BqU. U.S. Nat. Mus. xlvii. 1900, p. 2784'. 

 Ilah. Mexico, San Juan Lagoon in Sonora i. 



3. Arius fuerthii. (Tab. XVIII. fig. 2 and Tab. XIX. fig. 8.) 



Arius furthii, Steind. Sitzungsb. Ak. Wien, Ixxii. 1876, p. 579 \ 



Tachysurus furthii, Jord. & Everm. Bull. U.S. Nat. Mus. xlvii. 1900, p. 2787 - ; Gilb. & Starks, 



Mem. Calif. Ac. Sci. iv. 1904, p. 32'. 

 Tachysurus sttindachneri, Gilb. & Starks, t. c. p. 29, t. 5. fig. 9'. 



Depth of body 5 in the length, length of head 3| to 4. Breadth of head Ij in its length, diameter of eye 

 to 74. Fontanel produced into a groove which does not reach the parieto-occipital ; occipital process 

 with or without a weak keel, usually broader than long, with straight or concave sides and truncate or 

 emarginate apex; dorsal shield small, subcrescentic. Width of mouth | the width of head; praemaxillary 

 band of teeth 4 times as long as broad ; teeth on the palate obtusely conical, in 2 rather large subovate 

 patches which are not very widely separated anteriorly ; maxillary barbel extending to the basal part or 

 middle of pectoral. 10 or 11 gill-rakers on the lower part of the anterior arch. Dorsal 1 7 ; spine 

 I to I the length of head ; adipose fin shorter than the dorsal. Anal 20-24. Pectoral spine -| to | the 

 length of head, with the inner edge moderately serrated. 



Hah. Panama ^ ^ s 4 (^Boucarrl, Jordan). 



Here described from five specimens, 190 to 260 mm. in total length. 



4. Arius evermanni. 



Tachysurus evermanni, Gilb. & Starks, Mem. Calif. Ac. Sci. iv. 1904, p. 3.2, t. 5. fig. 10'. 



Hah. Panama i. 



Very closely allied to A. fuerthii, but apparently distinguished by the shorter and 

 broader occipital process. 



The species is based on a single specimen of 250 mm. 



