SOUTH AMERICAN NEMATOGNATHI. 437 



XC. Delturus. 



Belturus Eigenm. & Eigenm. Proc. Cal. Acad. Sci. 2d 

 Ser. ii, 45, 1889 (parahyhw). 



Type: Delturus parahyhca Eigenm. & Eigenm. 



This genus is most closely allied to Hemipsilichthys 

 from which it differs in its long adnate dorsal fin and the 

 greater development of its lateral plates. The tail is flat 

 below, trenchant above; a cross section being /^-shaped. 

 The sides of the head with short fine bristles w^hich do 

 not encroach on the preopercle. 



Habitat: Rio Parahyba; Rio Mucuri. 



ANALYSIS OF THE SPECIES OE DELTURUS. 



a. D. I, 9. Fius plaiu; lat. 1. 24; depth of head less than one-half of its 

 width. anrjuUcauda 411. 



an. D. I, 10. Fius all spotted; lat. 1. 25-27; depth of head less than one 

 half of its width. parahybce 412. 



411. Delturus angulicauda. 



Pkcostonius angidirauda Steiudachuer, SB. Ak. Wien, Ixxiv, 1876, 

 Stisswasserfische Sitdostlichen Brasilieus, iii, 114, jDlate xii, (Rio 

 Mucuri near Santa Clara; ? Rio Parahyba). 



Delturus angulicauda Eigenm. & Eigenm. 1. c. (Santa Clara, Rio 

 Mucuri). 



Habitat: Rio Mucuri and ?Rio Parahyba. 



Head and anterior portion of the body depressed, the 

 greatest depth of the body If in its width; tail strongly 

 compressed, flat below, trenchant above. None of the 

 plates on the snout enlarged. Occipital bone subtrian- 

 gular margined by a single nuchal plate; a naked area 

 behind the temporals. Margin of the snout to the inter- 

 opercle with short fine bristles. 



Interorbital flattish or strongly concave, the supercil- 

 iary edge raised, margined with short bristles. Eye 3| 

 in the snout, 5|-5i in the head, If-lf in the interorbital. 



Teeth large, the tips equal lobed. 



A few granules behind the gill-openings, ventral sur- 

 face otherwise naked. Plates on the lower surface of the 



