138 CALIFORNIA ACADEMY OF SCIENCES. 



c. Color plain; occipital process minute; eye small, turned ixpward, 

 much nearer snout than to posterior margin of opercle, 6-7 

 in head, 2 in the interocular; posterior nares much nearer the 

 eye than to the anterior nares. Width of mouth 2 in head; 

 jaws equal; maxillary barbels do not reach beyond tips of 

 pectorals, postmentals not bej'^ond their base; base of dorsal 2 in 

 its distance from the adipose which begins behind the vertical from 

 the insertion of the anal and reaches to the caudal. Pectoral spine 

 smooth, about 3 in head; dorsal spine shorter but not stronger 

 than the rays; caudal fin slightly emarginate. Grayish with darker 

 markings. Head 5 in the length. D. I, 5-6; A. 16-18. (Liltken.) 



microcephala 97. 

 cc. Back and dorsal fin with numerous small black spots. Dorsal 

 spine produced in a filament; dorsal and anal fins concave. Max- 

 illary barbels extending to ventrals. Adipose fin scarcely longer 

 than the dorsal fin. Br. 9; D. I, 6; A. 17. Vertebrae 44. Grows to 

 large size. (Schomburgk.) notata 98. 



bb. Adipose fin twice as long as anal. Eye large, nearer edge of opercle 

 than to tip of snout. Maxillary barbels extending scarcely beyond 

 head. Depth of intermaxillary band of teeth about 4 in its width. 

 A. 15. eriarcha 99. 



aa. A. 9-14. 



d. Jaws equal; nvimerous pores about the head. Maxillary barbels ex- 

 tending to a point between the ventrals and anal. Eye elliptical, 5 

 in head, 2 in interocular, nearer snout than to opercular margin, 

 Humeral process one-third as long as pectoral spine. Adipose fin IJ 

 times as long as the dorsal; caudal lobes equal. Dark brownish, with 

 traces of a longitiadinal band; no spot on adipose. Head 5; depth 5; 

 D. I, 7; A. 13-14. (Jenyns.) exsudans 100. 



dd. Upper jaw longer than lower. 



e. A dark lateral band; occipital j^rocess moderate. 



/. Dorsal spine very weak, low, 2^-2| in head; pectoral sj^ine 2-24 



in head; caudal fin 44-5^ in the length (Mexican). parryi * 



ff. Dorsal spine strong, high, l^-lf in head; pectoral spine 1J-1| 



in head; caudal fin about 3f in the length. jenynsii 101. 



ee. Several dark cross-bars, or plain; occipital process minute; head 



short, 5 in the length. minnta 102. 



97. Rhamdella microcephala. 



Rhamdia mkrocejthala (Rheinhardt MS.) Llitken, Dan. Selsk. Skr. 



177, pi. iii, fig. 7, 1875 (Eio das Velhas). 

 Habitat: Eio das Velhas. 



This species is known only from the types; it is most 

 nearly related to R. notatus (Schomb.) and R. laticauda 

 Kner. 



* Rhamdia parryi Eigenm. & Eigenm. Proc. Cal. Acad. 2d Ser. i, 130, 1888 (Rio Zanaleneo; 

 Chiapas; Mexico). We have dedicated this species to Dr. C. C. Parry of Daveuport, Iowa. 



