306 PROCEEDINGS OF THE ACADEMY OF [Oot.-NoV., 



modified at the first annulus. In Colpichthys further, the scales 

 are rather thicker and larger than in Atherinops, the number of trans- 

 verse series 47 to 51, instead of 52 to 72. 

 (Colpichthys, a fish of the bay or gulf.) 



THYRINOPS new genus. 



Genotype. — Atherinichthys pachylepis Giinther, 1864 ( = Menidia 

 pachijlepis Jordan and Evermann 1896 = Thyrina pachylepis 

 Jordan and Evermann 1898, and Regan 1907 = Kirtlandia pachy- 

 lepis Gilbert and Starks 1904). 



Thyrinops pachylepis, the only species of the genus, occupies a 

 position almost exactly intermediate between Kirtlandia and Athe- 

 rinella, agreeing with both of these genera as well as with Menidia, 

 etc., in the posterior position of the anal fin, which is not advanced 

 as in Thyrina and Eury stole. Thyrina closely resembles Thyrinops, 

 and is probably a fresh-water derivative from some such form. 

 This conclusion is strengthened by the fact that some species of 

 Thyrina, especially T. sardina, have the scales on the sides more or 

 less laciniate. 



Thyrinops may be diagnosed as follows: form moderately slender, 

 contracted ventrally as in Thyrina. Head rather pointed; gape 

 strongly arched downward posteriorly; jaws forming a semicircular 

 curve when viewed from above; maxillary not reaching to below 

 front of orbit. Teeth in villiform bands, rather wide in the upper 

 jaw, but narrow in the lower; outer series of premaxillary teeth 

 spaced and a little enlarged; entire palate toothless. Scales thick- 

 ened, rather deeper than long; the free margin rounded, but the 

 dorsal, ventral, and basal margins nearly straight; circuli absent 

 from the apical field, which is crossed by numerous fine, subparallel 

 radii, between which the scale is produced so as to form a border 

 more finely laciniate than in Membras (Kirtlandia) ; basal field usually 

 crossed by a line or two along which the circuli are curved inward; 

 basal radii usually absent on the trunk scales, or only a few shallow 

 ones developed, whereas on the tail the scales are deeply sculptured 

 with well developed radii ;^ The number of scales is about 40 in 

 lateral series. Fin rays: dorsal, IV or V-I, 6 to 8; anal I, 20 to 23. 

 Anal base decidedly longer than head, as in Thyrina; soft dorsal and 

 anal fins scaleless, falcate in outline; origin of spinous dorsal well 

 behind that of the anal, about an orbital length separating the two 



1 This variation has been entii'ely too much neglected in recent studies of fish 

 scales, not so much in this family as in other groups. 



