136 Bulletin ^.y, Untied States JVattonal Mnscuni. 



backward prolongation at the angle. Dorsal between the pectorals and 

 ventrals higher than long, with a pungent spine and about 6 branched 

 rays. Adipose fin short, inserted over the posterior half of the anal. 

 Anal fin of varying length, with 15 to 35 rays, the usual number being 

 20 or 21. Caudal fin short, truncate in typical species, more or less 

 forked in those species which approach the genus Ictalurus. Ventrals 

 each with 1 simple and 7 branched rays. Pectoral fins each with a stout 

 spine, which is commonly retrorse serrate behind. Lateral line usually 

 incomplete. Species very numerous, swarming in every pond and slug- 

 gish stream in the Eastern United States; especially characteristic of 

 quiet waters; 1 species (A. cantonetisis ) in China. The species are 

 variable and not easily distinguished. Those in which the caudal fin is 

 forked make an approach to the genus Ictalurus. The lack of connection 

 between the supraoccipital and the interspinal buckler is the only char- 

 acter by which these species can be separated from Ictalarus, of which 

 group Ameiurus should perhaps be regarded as a section, (u, privative; 

 iiEiovpoQ, curtailed; the caudal fin not notched.) 



Haustou, [haustor, one who swallows): 

 a. Caudal fin lunate or forked; occijutal process produced backward, not falling far short of 

 the interspinal bones; species of large size, approaching Iclahtrus; coloration more or 

 less grayish or silvery. 

 h. Anal rays 25 to 35; humeral process very short and blunt, usually covered by skin, 

 about }<2 length of pectoral spine. lacustris, 209. 



!*. Anal rays usually 20 to 22 (19 to 24). 



c. Base of anal fin longer than head; head rather narrow, the bony occipital briilgc 

 almost complete. litpv.s, 210. 



ce. Base of anal fin much shorter than head. 



d. Humeral process strongly rugose; head and mouth narrow in young, becom- 

 ing very broad in the adult. catus, 211. 

 (Id. Humeral process slightly furrowed; head narrow. dugesi, 212. 

 hhb. .\nal very short, of about 16 rays, its liase not J length of body and little more 

 than y^ head; head broad, with long barbels. okeechobeensis, 213. 

 Ameiurus: 

 aa. Caudal fin entire, truncate or very slightly marginate behind. Eyes well developed. 

 Coloration, brown or yellowish, not silvery. 

 e. Anal fin long, of 22 to 27 rays (counting rudiments), its base more than J4 body, 



/. Head and body elongate, the back high, the head much longer than broad; pecto- 

 ral and dorsal spines very long. erebennus, 214. 

 ff. Head and body robust, the back low, the head not much longer than broad, 

 pectoral and dorsal spines moderate. natalis, 215. 

 ce. Anal fin moderate or short, of 15 to 22 rays, its base 4 to 6 in the body. 



g. Lower jaw projecting; anal rays 20. vulgaris, 210. 



gg. Lower jaw not projecting. 



h. Body rather robust, the depth in the adult 3}^ to 4^^ in length; head not 

 very flat above. 

 I. Pectoral spines long, 2 to 2}^ in bead; anal rays more than 20. 



nedulosus, 217. 



ii. Pectoral spines short, 2^^ to 3 in head, longest in young. Anal fin 



shorter, of 17 to 19 rays counting rudiments. melas, 218. 



hh. Body slender and low, varying with age, the depth 5)^ to 8 times in length; 



head in adult broad and very flat; anal short, usually with 18 or 19 rays; 



a broad dusky shade across the base of dorsal which is rather high. 



PLATYCEPHALUS, 219. 



Ghonia-s, (yp<ovi), a cavern): 

 aaa. Caudal fin entire; eyes covered by thick skin. 



j. Color chiefly black. HIGBItABEls, 220. 



