26 CALIFORNIA ACADEMY OF SCIENCES 



sides ami belly, almost eiitiicly miiskiii<i llio silvorv of (lioso |iiiifs. In otlicr spoci- 

 meiis, the iriiles nml l)elly are brij^lit silvt-i y witlioiit l)r()\Yii liiij;o. Tlic fins arc all 

 ilusky, ill some specimens much darker than in others; the ventrals soiuetimcs nar- 

 rowly cductl with hrijjht wliiio. 



We have been tempted to consider this species the male of G. (lamjce/thnlni^, 

 as oiir niimcrons specimens seem to be all males, while onr specimens of G. d/txy- 

 cephii/iix, as well as all those of which we have record, seem to he females. The 

 structural dilTereiices are so nuich greater in .iniounl llinii aic known lo l)c scxnal 

 with any other species, that we hold the two forms distinct. In addilion In llic j-lrikinj,' 

 dilTercnce in the lenjith and scidptni'lnj; of the head, (i. l'iii;/icv/)/iit/ux has shorter 

 barbels, coarser j;ill-rakers, shorter pectoral spines, a wider fontanel, and a wider 

 snout niul mouth. 



38. Sciadeichthys troscheli (dUI). 



Abundant aloni; the entire coast of IMexico and Central Ameiica. At 

 Panama it occurred daily in the niarkcls, l)nt seldom in large niiinlicrs. The collec- 

 tion contains five specimens from Panama, one from Champerico. 



The species varies in certain respects more than has been represented. The 

 dor.sal l)nckler varies much in width, and even in general shape; one specimen at 

 hand has it triangidai', tapering nearly uniformly from the base forward to the long 

 acute apex, two-fifths of its length on the median line being contained within the 

 notch of the occipital process. In one individual, the granulations are very sparse, 

 and largely obscured by the thickened integument. 



The maxillary barbels are blackish, with a consj)icuous white infeiior mar- 

 gin. They vary much in length, often failing to reach opercular opening, sometimes 

 overlapping base of pectoral spine. The vomerine patch of teeth is sometimes long 

 (transversely) and narrow, thus separating widely the palatine bands (as figured by 

 Eigenmann and Eigenmann, 1890, p. 56); sometimes much shorter and wider. The 

 head seems very constant in length, 3^ to 3,'; in total length (without caudal). 



39. Selenaspis dowi {Gill). 



Large specimens are frequently brought into the Panama market, but seldom 

 more than two or three at a time. The young are rarely seen. In one of the speci- 

 mens at hand, a curious variation is observable in the shape of the dorsal shield, which 

 has its anterior margin medially produced and wedge-shaped, fitting into an 

 emargination in the occipital process, much as in Sciadeichthys troscheli. 



40. Netuma kessleri (Steindachner) . 



One of the most abundant species of catfishes at Panama. It varies in color 

 from light brown to nearly black on the upper parts, and may be pure white below 

 or variously marked with brown. The fins vary in a similar manner, the caudal, anal, 

 and inner surfaces of pectorals and ventrals being black in the darkest specimen.s, 



