438 CALIFORNIA ACADEMY OF SCIENCES. 



tail smooth, covered with skin; other plates with dentic- 

 ulate ridges which terminate in rather large marginal 

 spines. 



Last dorsal ray joined to the back by a membrane. A 

 series of three trenchant azygous plates between the dorsal 

 and adipose fins. 



Caudal obliquely truncate. 



Pectoral and ventral spines thick, covered with num- 

 erous short bristles; the pectoral reaching little beyond 

 base of ventral; the ventrals to the anal. 



Light brown; the fins all plain. 



Head3-3i; Lat.l. 24; D.I, 9; A. 6; V. 1,5; P. I, 6. 



One specimen .27 m. Santa Clara, Rio Mucuri. 



412, Delturus parahybse, 



Delturus parahybce Eigenm. & Eigenm. Proc. Cal. Acad. 2d Ser. ii, 

 45, 1889 (Parahyba). 



All the fins with large, round, blackish spots. 

 Lat.l. 25-27; D. 1, 10. 



Types No. 7726, two specimens .28 m. Parahyba. 

 Thayer expedition. 



XCI. HE.MIPSILICHTHYS. 



Xenomystus Liitken, Vid. Medd. 1873, No. 13, 217, pi. 

 iv, (gobio), name preocupied in Ichthyology 1868. 



Hemipsilichthys Eigenm. & Eigenm. Proc. Cal. Acad. 

 Sci. 2d Ser. vol. ii, 46, 1889 (gobio). 



Type: Xenomystus gobio Liitken. 



This genus is closely related to Pseudancistrus. There 

 is a naked area behind the dorsal fin, several highly keeled 

 azygous plates in front of the adipose spine. Tail com- 

 pressed, flat below, the plates covered with skin. Bases 

 of the lateral plates concealed beneath the skin. Dorsal 

 short. 



413, Hemipsilichthys gobio. 



Xenomystus yobio Liitken, 1. c. (loc. ?). 



HemipHilichthys gobio Eigenm. & Eigenm. 1. c. (Kio Parahyba). 



Habitat: Kio Parahyba. 



