36 Synapsis of the Fresh Water Fishes, 



recede from each other at an angle less than a right angle, and 

 are extended backwards for some distance, when they are ter- 

 minated by a more or less rounded angle, from which they 

 advance obliquely upwards and forwards to the mastoid plates; 

 the sides of the breast are thus protected by these plates, and 

 the interval or bare skin of the breast between them, is of a 

 more or less elongated triangular form. 



This genus is framed for the species of Callichthyinse with the 

 head depressed, and with the breast protected by the humerals. 

 The Callichthys Isevigatus of Valenciennes, of which the C. 

 subulatus of the same author is the male, may be considered 

 as its type. The remaining species are C. littoralis of Hancock, 

 which appears to be distinct from C. Isevigatus, C. albidus, Val., 

 C. chiquitos, Castelnau, C. thoracatus, Val., and C. longifilis, 

 Val. The C. personatus of Ranzani, and C. sulcatus of Kner, 

 appear to be synonymous with the latter species. 



Hoplosterniini laeTig^atum, (Val.) Gill. 

 Vernacular; Casoadura. 



SYNONYMY. 



Callichthys laevigatus, Val. Hist. Nat. des Poissons, vol. 15, p. 314, 



(female.) 1840. 



This species is very variable in its proportions, in the length 

 of the spinous rays of the pectorals, and in the extent and width 

 of the naked skin which intervenes between the frontal plates. 

 It rarely reaches a length of more than five or six inches, of 

 which the height generally forms considerably less than a quar- 

 ter. The head bears a variable proportion to the greatest 

 height of the body, the latter being sometimes less, and some- 

 times greater than the length from the muzzle to the margin 

 of the operculum: the height is always greatest at the first 

 dorsal spine, from which point the profile descends, with a very 



