Jordayi and Ever7na?in. — Fis/ies of North America. 3139 
distal parts soft, not branched, continuous with the hard parts; basal 
jiart of pectoral siiine grooved posteriorly, weakly serrate above the 
groove. 
Isilariiis has some of the characters of the genus Leptops, notably the 
dentition of the upper jaw and the weakness of the tin-spines; but it 
more closely resembles Ictahinis, and its relationship is probably with 
that genus. 
(Named for the Rio Ixtla, the type locality of the type S2>ecies. ) 
20S (a). ISTLAKIUS BALSAXUS, Jordan & Snyder. 
Head 4; depth 4|; depth of caudal iieduucle in head; eye 54; snout 
2|; distance between eyes 24; heiglit of dorsal 1|; length of base of 
dorsal 3; height of anal Ij; length of base of anal 1; length of pectoral 
14; A'eutrals If; caudal 1; D. I, 6; A. 24. Body deep and somewhat com- 
jjressed, dce^iest above ventrals, widest between pectorals; head narrow, 
not greatly depressed; eye large, nearer tij} of snout than to posterior 
edge of opercle a distance equal to diameter of eye; iuterorbital space 
convex; width of mouth 2f in head, lower jaw included; upjier jaw pro- 
jectiug a distance equal to diameter of jiupil; barbels 8; of the inferior 
ones the median jjair shorter; distance between their bases equal to the 
diameter of pujiil; the outer jiair when extended directly backward reach 
the edges of gill covers; maxillary barbels longest, reaching upper angle 
of gill opening; nostril barbels reaching middle of pupil. Teeth in broad 
villi foVm bands on premaxillaries and dentaries, the baud on up^ier jaw 
convex anteriorly, with a short, angular jiosterior extension on each side, 
no apparent division of the baud at symphysis; baud on lower jaw broad 
anteriorly, narrow and pointed x^osteriorly, a distinct median division; 
no teeth on A'omer or palatines ; upjier jiharyngeal teeth in oval villiform 
bands; lower pharyngeal teeth in 2 narrow oblong bands; gill-rakers 
on first arch 17, long and slender; brauchiostegals 8; anterior nostril 
tubular, the posterior with a raised rim extending on each side from the 
btirbel to the jiosterior edge of the oiieuing, where it is divided; skin of 
head completely concealing the Imues of skull; supraoccipital l>one not 
in contact with inters|iiual ; humeral jirocess about as long as vertical 
diameter of eye, almost hidden by the thick skin; lateral line extending 
from a perpendicular through insertion of dorsal to caudal; skin covered 
with minute, hair-like villi ; dorsal spine Avith its distal third soft, jtre- 
ceded by a small, angular, immature sjAine; iirst branched ray longest, the 
others gradually shorter; adiiAOse fin large, aboA'e middle of anal; length 
of the jAosterior free edge 3 times diameter of pupil; third or fourth anal 
ray h.mgest, edge of fin rounded ]>osteriorly ; caudal Alcejily i’orked, the 
lower lobe rounded, the ui)])er rather jiointed ; i»cctoral rays I, 11, distal 
two-thirds of sjAine soft, not branched, continuous A\'ith the hard ]>art ; 
basal jiart grooved posteriorly, Aveakly serrate above the groove; Aentrals 
reaching origin of anal. Color bluish slate aboA e. light silveiy beh)AA’’ ; a 
feAV small dark s]>ots on the head and body; fins Avith dusky coloring; 
inferior barbels light; maxillary barbels Avith ujq)cr halt dark; nasal 
barbules AA'ith light edges. Some speciimuis ha\'e m.any Avell-delined color 
