99 FISHES OF SINALOA. 47I 



a substitute for Gerres, regarded as preoccupied by the 

 earlier name Gem's, applied by Fabricius to a genus of 

 insect's. The name CatochtBtium can only be used if 

 Gerres is regarded as ineligible. By the rules followed by 

 us, Gerres must be retained, being spelled differently from 

 Gem's. In different publications of Poey, phonier! is 

 made the type of Gerres, although it is not one of Cuvier's 

 original species. Bleeker substitutes Diapterus for Ger- 

 res and ( 'atoclncnum. specifying -plumierizs its type, while 

 Gill and Poev have used the name Diapterus for the allies 

 of gula, to which the name JEucinostomus had been applied 

 in 1855 by Baird and Girard. Although plum ieri cannot 

 be made the type of Gerres, it seems to us that the cog- 

 nate species I i neat us can be so regarded. If this view is 

 adopted, the restricted Gerres of the present paper would 

 correspond exactly with the restricted Gerres of Poey and 

 Gill. This fact certainly justifies us in choosing I in cat us 

 as the type of the genus. 



There can be no doubt of the generic value of Eucin- 

 ostomus (gula) and of Ulcema Jordan & Evermann MS. 

 (lefroyi), as distinguished from Gerres. Of the other 

 groups represented in American waters, Xystcema Jordan 

 & Evermann MS. (cinereus) seems to be a valid genus, 

 while Diapterus (auratus) should stand rather as a sub- 

 genus of Gerres. Diapterus differs from Gerres chiefly 

 in the entire preorbital. Xystcema has the preopercle as 

 well as preorbital entire, while Ul tenia has the second in- 

 terha^mal very short, and the two spines of the anal are 

 themselves scarcely enlarged. 



Moharra Poey (rhombeus) differs from Diapterus only 

 in the presence of two anal spines instead of three, a 

 character of low importance, as the relation of the species 

 included in the two groups is very close. 



The exotic genera of this group have not been studied 

 by us. 



