11 



BULLETIN :5G, UNITED STATES NATIONAL MUSEUM. 



(Vimiuishccl by the fact that the specimen of S. brasilicmls is very youug. 

 Tlio characters drawn out b3^ M. Ed. Van Beneden are as follows : 



Cbaracters. 



1 . Size 



2. Number of vertebnn 



3. Number of ribs (pairs) 



4. Number of sternal ribs (pairs) 



5. Number of pieces in sternum . 



G. Number of teotb 



7. Ear-bones 



S. guiancnsis. < S. brasiliensis. 



greater. 

 55 

 12 



7 



3 



32 



C 32 



( 29 



29 

 smaller. 



smaller. 



54 



11 



C 



jl (of bone); 



(1 (of cartilage). 



34 



33 

 lar g e, r and 

 peculiar. 



On account of the immature condition of the specimen of ^. hrasiliensis, 

 characters 1 and 5 are manifestly of little importance. The differences 

 represented in characters 2, 3, and G are within the range of individual 

 variation, as has been abundantly proved by the examination of various 

 species. Characters 4 and 7, therefore — the number of sternal ribs and 

 the size and form of the ear-bones— alone constitute recognizable dis- 

 tinctions between the two species, Of these two characters, the first is 

 quite likely to be merely an individual difference; but the second cau 

 not of course be so considered. 



Between S. JiiiviatUls and ;S^. pallida the following distinctions are 

 made: 



Color— 



S. JliiviatiUs : Body black above, roso-piak below; pectorals colored llko the back. 



S. pallida : Body fulvous above, white bolow ; pectorals not colored like tbe back. 

 Pectoral lius— 



S. fluvlatiUs : Quito large and pointed. 



S. pallida : Smaller, less pointed, and narrower at the baso. 

 Dorsal fin — 



S. fluvialilis : Two-thirds as high as long. 



S. pallida : Less high. 



These distinctions are unsatisfactory, but cau not be set aside without 

 reason. 



Between the five species we have but two points of comparison, the 

 color of the body and the number of teeth. The data given by the dif- 

 ferent original dcscribers are as follows: 

 S. hra-'iilicnsis — 



Color: Back blackish, sides fulvous, belly white; pectoral like the back, 

 Teeth : ^^ (E. Van Beneden.) 

 S. {juianetisis — 



Teeth: f|. (E. Van Beneden.) 



S. itlCHXi — 



Color: Darkish black or fuscous. Teeth: jj;]. (Gray.) 

 S.Jluviatilis — 



Color: Above black, beneath rose-color; pectorals like the back. (Gcrvais.) 

 S. pallida — 



Color: Above fulvous, beneath white; pectorals like the belly. Teeth: |^. 

 (Gervais.) 



