18S7.1 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 71 



4. Archosargus tridens. 



Sar(ju8 tridens Poey, Enumeratio Pise. Cub., 57, 1875 (Cuba). 



Habitat. — Ciib.a. 



This species is knowu to us ouly from the description of Professor 

 Poey. Its distinctive characters need verification, it being perhaps an 

 abnormal specimen of Archosargus unimaculatiis. 



3. DIPLODUS. 



DiPLODUS Rafinesqne, Indice d'lttiologia Siciliaua, 54, 1810 (annularis), 

 Sargus Cuvier, Regue animal, 1817 {sargus), (uaine preoccupied). 



Type. — Sparus annularis Gmeliu. 



The name Diplodus should of course sui)ersede Sargus both from the 

 fact that it is prior in date and because the latter name has been earlier 

 used for a genus of insects. The genus Diplodus, as here understood, 

 differs from Archosargus chiefly in the absence of a procumbent dorsal 

 spine. 



Most of the species of Dijjlodus are European, as those of Lagodon, 

 Archosargus, and iStenotomus — the genera which have the procumbent 

 dorsal spine — are American. The skull in Diplodus resembles that of 

 Archosargus, but the cavernous or honey-combed structure of the in- 

 terorbital area is still more prominent. 



Skeleton of Diplodus annularis, type of Diplodus. — Vertebrte 10 + 

 14. No procumbent spine before the dorsal fin. Upper surface of the 

 skull very rugose, with many ridges ; occipital crest extending to 

 frontal bone ; frontal crest a mere ridge in the interorbital area ; the 

 bony stay extending on the occipital crest up from the posterior edge of 

 the skull more prominent than in others ; a crest extending from the 

 upper angle of the preopercle, forward to anterior edge of occipital 

 crest; this crest is broad and porous posteriorly ; the inner edge is well 

 defined, the outer edge with many projecting points. A smooth, thin, 

 but higher crest extends between this and the occipital crest from the 

 insertion of the scapula forward to the transverse crest. The interor- 

 bital not rounded, with many irregular crests. Maxillary without fora- 

 men. Teeth somewhat abruptly narrowed. 



ANALYSIS OF SPECIES OF DIPLODUS. 



a. Scales, 7-5G-14 ; depth iu adult, 2^ in length ; black bar extending entirely across 

 caudal peduncle ; body regularly elliptical, moderately compressed ; bead 

 3| iu length ; profile reguarly rounded, not as steep as in argenteiia; eye 

 1£ in preorbital ; 1^ in snout ; 4| iu head ; mouth large, almost horizontal; 

 maxillary 3^ in head; incisors |, inserted obliquely; molars iu 3 series 

 above and 2 below ; longest dorsal spine Sf in head ; caudal deej)ly forked ; 

 second anal spine little larger than third, 3^ iu head; ventrals reaching 

 half way to the anal fin ; pectorals not reaching to first anal spiue ; steel- 

 blue above, paler below, abroad black border on the operculum ; a black 

 spot on upper part of base of pectoral ; D. XII, 14 or 15 ; A. Ill, 13. 



HOLBROOKI, 5. 



