284 THE PLAGIOSTOMIA. 



Subcaudal narrow, rounded below. Scales minute, sharp-edged or acute, smooth 

 or with low carinae. Small tubercles above the vertebrae, in two groups on each 

 shoulder, above the orbit and the spiracle and on very young individuals in a 

 series above each of the rostral ridges. Old specimens have all of the tubercles 

 comparatively smaller. 



Dark brown, in cases clouded, with or without small spots of white, sym- 

 metrically arranged, along the back, Plate 17a, fig. 3, fins and edges of disk lighter, 

 snout at the sides of the rostral cartilage white; lower surface white, with or 

 without a black spot below the end of the snout. 



Peru to the Galapagos Islands. 



Syrrhina. 



Syrrhina (subgenus) Muller & Henle, 1841, Plagios., p. 113 (part). 

 Zapteryx Jordan & Gilbert, 1880, Proc. U. S. nat. mus., 3, p. 53. 



Disk subround, broader than long; snout short, broad; tail more than half 

 the total length. Rostral cartilage strong, tapering with ridges convergent 

 but not confluent to shovel-shaped with ridges nearly parallel. Nostrils nearly 

 transverse; anterior valve extended on the internarial space. Mouth arched; 

 upper lip distinct in front of the middle. Spiracles large, near the eyes. Pec- 

 torals broadly expanded posteriorly, but little continued in the snout. Ventrals 

 close to the pectorals, claspers knobbed at the end. Tail rather slender, with a 

 fold on each side; supracaudal fin longer; subcaudal not lobed. 



The subgeneric rank of Syrrhina was claimed by Muller and Henle on ac- 

 count of the extension of the anterior nasal valve on the interspace. As noted 

 by Gunther, this is a feature that varies much in the species of Rhinobati. In 

 fact, as may be seen from the descriptions herewith, on nearly or quite all of 

 these species the inner end of the valve is started beyond the nostril for a short 

 distance. The generic rank was claimed later because of the broader, rounder 

 disk, from greater development and forward extent of the pectorals, the short- 

 ness of the snout, the transverse nostrils, and the greater proportional distinc- 

 tion between tail and disk. The genus contains but one of the species placed by 

 Muller and Henle in then - subgenus; two others are added. 



Brazil; California to Panama. 



Pectorals extending nearly halfway from nostrils to end of snout 

 rostral ridges converging forward 



coloration uniform or clouded with brown . brevirostris (page 285) 



