340 CALIFORNIA ACADEMY OF SCIENCES. 



Yellowish; posterior half of the caudal fin dusky; a 

 series of black spots along the base of the anal. 

 Head 9; depth 13; D. 10-12; A. 20-25. 



276 Tridens brevis- 



Tridens hrcvls Eigenm. & Eigenm. Proc. Cal. Acad. 2d Ser. ii, 54, 



1889 (Tabatiuga). 

 Type, No. 8160; one sjiecimeu; .021 m. Tabatinga. Boiirget. 



Body short and deep. Head as broad as long; mouth 

 broad, inferior. Opercle with a bunch of six or more 

 spines; preopercle with a smaller bunch of spines. Bar- 

 bels well developed, the outer one extending to the base 

 of the pectoral, the inner to the gill-opening. Eye large 

 nearer end of opercle than tip of snout. 



Distance of origin of dorsal from tip of caudal little 

 more than 2 in the length. 



Anal inserted very little in front of the dorsal and ex- 

 tending some distance beyond it, its rays decreasing in 

 height toward the caudal. Origin of anal from extrem- 

 ity of caudal less than 2 in the length. 



First pectoral ray greatly produced. 



Caudal emarginate. 



Yellowish; blackish dots along the bases of the fins; a 

 series of blackish dots along the middle line of the 

 sides, similar spots on the back. Head with brown dots. 



Head 6; depth 8; D. 9; A. 22. 



The two species here described have evidently not at- 

 tained their full growth. They may prove to be the 

 young of some species of Pygidium. If so their char- 

 acters undergo a wonderful change during growth. 

 As nothing is known of the young stages of these fishes 

 we have thought best to describe these specimens as new. 

 They approach the P. amazonicum Steindachner, from 

 the Jutahy most nearly. 



