GENUS SEBASTODES. 585 



nial characters, summarizes what has been said and in- 

 cludes some details not hitherto mentioned : 



A. Base of skull markedly curved. luterorbital space convex or flat, 

 broad, less than 3^ in the base of the skull. Processes of mesethmoid 

 not directed upward. Ventral process of basisphenoid rtidimentary. 

 Cranial ridges obsolete or weak, spines absent or delicate. 



a. Cranial ridges (except jparietal) obsolete or very slightly developed. 

 Cranial spines absent or very inconstant and weakly developed, 

 b. Parietals not meeting; mesethmoid processes weak and depressed; 

 skull moderately thick; parietal ridges weak, with minute spines 

 or none; other ridges none. 



c. Interorbital space plainly convex, paucispinis. 

 cc. Interorbital space nearly flat, goodei. 



bb. Parietals meeting in the middle line, but separated posteriorly 

 by a wedge-shaped exposure of the supraoccipital. Mesethmoid 

 processes better developed, straight and horizontal; skull thick; 

 the bones striated; parietal ridges low, spineless, other ridges 

 none. 



d. Preocular spines none, flavklus, melanops. 

 dd. Preocular spines present, mystinus. 



aa. Cranial ridges somewhat developed; preocular, supraocular, post- 

 ocular, tympanic and parietal spines present, all delicate; ventral 

 process of basisphenoid sometimes present in young. (Tympanic 

 spines usually absent or imperfect in airovirens.) 

 e. Parietals not meeting; interorbital space usually plainly convex; 

 bones thick, more or less striated, 

 f. Supraocular spine present. 



g. Base of skull strikingly curved; parietals nearly meeting, 



entomelas, ovalis. 

 gg. Base of skull less strikingly curved; parietals well separated, 

 h. Interorbital space plainly convex, jnnniger. 

 hh. Interorbital space flat or nearly so, miniatus. 

 ff. Supraocular spine absent; parietals well separated; interorbital 

 space but little convex; mesethmoid processes directed some- 

 what upward, atrovirens. 



B. Base of skull markedly curved. Interorbital space flat or slightly 

 concave, of medium width, 3f to 4^ in base of skull. Processes of 

 mesethmoid directed but little upward. Ventral process of basisphe- 

 noid rudimentary or fairly developed. 



h. Cranial ridges fairly developed, supraocular spines absent, skull 

 thin, papery, mesethmoid processes horizontal, 

 i. Parietals not meeting, saxicola. 

 ii. Parietals meeting, diplojjroa. 

 •2d See., Vol. V. ( 38 ) Octolier 1, 1895. 



