SCOMBRHXE-^AUXIDES 11 



oblique, large, the mandible projecting, its length uncertain but one-third 

 to one-half head. Second dorsal and pectorals mostly obliterated; anal 

 entirely so ; finlets all destroyed. Body formed about as in the mackerels, 

 apparently evenly covered with small, smooth scales, larger than in 

 Scombroid fishes generally, those of the pectoral region not modified 

 to form a corselet, as is the case in Auxis, THUNNUS, etc. ; twenty-five 

 to thirty scales between the place the lateral line should occupy and the 

 ventral edge. Scales on the narrow caudal peduncle apparently but little 

 smaller than those near the head. 



In the "Poissons Fossiles," V, part 1, 55, plate XXVII, Professor 

 Agassiz figures from the Upper Eocene of Monte Bolca, a mackerel-like 

 fish resembling our specimen almost exactly in all details, under the 

 name of THYNNUS PROPTERYGIUS. The name THYNNUS is preoccupied 

 and the smaller tunnies, once referred to it, now constitute the genus 

 EUTHYNNUS of Lutken, while the great tunny and the albacore are 

 placed in the genus THUNNUS of South. Our species belongs to neither. 

 Its dorsal fins are far apart and it has not the specialized corselet seen 

 in THUNNUS, while its vertebrae lack the extraordinary modification 

 which is characteristic of EUTHYNNUS, well figured by Lutken in "Spolia 

 Atlantica." 



Kramberger, in 1882, doubtfully referred Agassiz's THYNNUS PROP- 

 TERYGIUS to the genus Auxis Cuvier, and in this reference, the doubt 

 included, he is followed by Woodward (Cat. Fossil Fishes, IV, 464). 



But the species is much more related to the true mackerel or 

 SCOMBER. The only genera with the first dorsal short are SCOMBER 

 and Auxis, and Auxis has modified vertebras as in EUTHYNNUS, and 

 also a much more widely forked caudal fin. It has likewise a pectoral 

 corselet of modified scales, the rest of the body being nearly naked or 

 very minutely scaled. There are thirty-nine vertebrae in Auxis, and the 

 tail is more slender, with a single strong keel. 



In SCOMBER the scales are very minute, with no pectoral corselet. 

 The vertebrae are" thirty-one, and the caudal keel is double and much 

 smaller than in Auxis. The mouth is much larger than in Auxis, though 

 smaller than in our specimen. 



I propose the new genus, AUXIDES, with Agassiz's THUNNUS PROP- 

 TERYGIUS as type. It is distinguished from SCOMBER by the fewer 

 vertebrae, larger scales, stronger dorsal spines and more oblique mouth. 

 To this genus I refer my species, as AUXIDES SANCT^-MONIC^E. 



A fish in many ways similar to AUXIDES is described in a subsequent 

 paper by Jordan and Gilbert as TUNITA OCTAVIA. TUNITA has a shorter, 

 deeper body, tapering more rapidly backward, and stronger dorsal spines, 



