NO. 5 MYERS AND wade: ATHERINID FISHES 135 



brane between the jaws. Teeth of upper jaw small, pointed, slightly 

 curved, depressible; anteriorly in a narrow band of two irregular rows, 

 narrowing to a single row laterally. Lower teeth similar to upper. No 

 teeth on vomer or palatines. Gill-membranes not united, free from isth- 

 mus. Gill- rakers on lower limb of first arch 18-20. Pseudobranchiae 

 present. 



Dorsal III or IV-I, 9 or 10. First dorsal short, its spines flexible, 

 its origin over or slightly behind anal origin, midway between caudal 

 base and a point between the center and anterior edge of the eye. Origin 

 of second dorsal over about seventeenth anal ray, ending above last anal 

 ray. Caudal base to origin of second dorsal 3.25-3.32 in standard length. 

 Anal fin elongate, I, 26-29, its margin slightly falcate, its origin slightly 

 nearer caudal base than tip of snout. Caudal fin forked, lower lobe 

 slightly longer. Pectoral rays 13, the fin broad and short, its length 1.03- 

 1.1 in head. Ventrals I, 5, closely approximated, short, not reaching anal 

 opening, their insertion nearer anal origin than upper angle of pectoral 

 base. Inner ray of each fin joined by membrane to mid-line of abdominal 

 wall. 



Color of Guayaquil specimens much darkened by long preservation, 

 the band plumbeous. The North Chincha specimen is pale yellowish, the 

 lateral band bright silvery. Lateral band bordered above by a narrow 

 dark line, not or barely constricted on caudal peduncle. Scales above 

 lateral band with only a few small, punctulate spots. Caudal fin slightly 

 darker distally. First and second dorsals with a few minute, dark punctu- 

 lations along rays. Anal, pectorals, and ventrals colorless. Cheeks and 

 opercles silvery. Nape and interorbital dark. Tip of snout, lips, and ante- 

 rior portion of lower jaw finely speckled with minute dark spots. An 

 irregular group of larger dots on preorbital before anterior edge of eye. 



(Nocturnus, of the night, in reference to the nocturnal surface swim- 

 ming habits of this species, as observed by the senior author at the Chincha 

 Islands.) 



History of the species. — This is dealt with under Eurystole eriarcha, 

 above. 



Relationships. — A^. nocturnus is very closely related to A'^. nepenthe, 

 differing only in its somewhat larger size and in the characters utilized 

 in our key. The Guayaquil types are not in the best of condition. They 

 are brown and distorted, the fins of most of them are badly broken, and 

 the single small specimen collected by the senior author at North Chincha 

 Island is not in too good condition. In spite of the vast distance which 



