166 Field Columbian Museum — Zoology, Vol. V. 



b. Origin of spinous dorsal in front of origin of page 



the anal fin ; base of the anal usually shorter 



than head Chirostoma 166 



bb. Origin of spinous dorsal over or behind origin 

 of anal fin. 



c. Scales cycloid; iris silvery Menidia 181 



cc. Scales with crenate edges; iris black Melaniris 183 



aa. Belly before ventrals compressed to an edge; 



pectoral fin much longer than head Thyrina 184 



<><>. Chirostoma Swainson. 

 Chirostoma Swainson, Class'n Fishes, etc., 243, 1839. (Type, 



Atherina humboldtiana Cuv. & Val.) 

 Atherinoidcs Bleeker, Verhand. Batav. Gen., Japan, xxv, 40, 1853. 

 (Type, Atherina vomerina Cuv. & Val. = Atherina lunnboldt- 

 iana Cuv. & Val.) 

 Atherinichthys Bleeker, 1. c, 40. (Type, Atherina humboldtiana 



Cuv. & Val.) 

 Heterognathus Girard, Proc. Acad. Nat. Sci. Phila., 1854, 198. 



(Type, Atherina humboldtiana Cuv. & Val.) 

 Lethostole Jordan & Evermann, Bull. 47, U. S. Nat. Mus., 1896, 792. 



(Type, Chirostoma estor Jordan.) 

 Eslopsarum Jordan & Evermann, Check-list Fishes, 330, 1896. 



(Type, Chirostoma jordani Woolman.) 

 Body elongate, slightly compressed; mouth more or less oblique, 

 terminal; the upper jaw curved near its middle; premaxillaries very 

 protractile; spinous dorsal near middle of the body, in advance of 

 origin of anal fin; gill rakers rather long and slender, 14 to 27 on first 

 gill arch; peritoneum black; alimentary canal short, shorter than total 

 length of the body; vertebrae 36 to 44. 



KEY TO THE SPECIES OF CHIROSTOMA. 

 a. Scales large, less than 45 in the lateral series; page 



edges of scales entire (occasionally crenate in 

 bartoni) ; vertebrae usually less than 40 ; species 

 of small size. 

 b. Mouth small, very oblique; snout short, 4 in 

 length of head; base of anal equal to or 

 slightly longer than head; anal rays 16 to 18; 

 teeth very minute; scales with entire edges, 



37 or 38 in the lateral series jordani 169 



bb. Mouth larger, less oblique; snout longer, 2% 

 to 2> 2 A i n head. 



