90 PROCEEDINGS OF TllE ACADEMY OF 



mus xanthurus are said to be villiform, in a very straight band, and scarcely 

 perceptible, so that they had been stated to be absent. It is moreover affirmed 

 that M. Bosc, who had furnished to M. Lacepede the figure and notes on which 

 that naturalist had established the Leiostomus xanthurus, had sent for exami- 

 nation to Cuvier and Valenciennes the fish itself. 



Cuvier and Valenciennes having thus stated that both of the Leiostomi were 

 provided with teeth on each of the jaws, Dr. Dekay, in his "New York 

 Fauna, ? ' and Dr. Storer, in his "Synopsis," followed them. Dekay, in his diag- 

 nosis of the genus, not daring to disagree with Cuvier, describes the " teeth 

 in the jaws, even and excessively small," and "very minute denticulations 

 on the preoperculum ;" in the description of his Leiostomus obliquus, Dekay 

 again states that the teeth are "so minute as to be visible only with a lens," 

 and that the preoperculum is " minutely denticulate." Dr. Storer adopted 

 the generic diagnosis formulated by Dekay. 



Dr. Holbrook subsequently framed for a new species and the Leiostomus 

 xanthurus of Cuvier and Valenciennes, and their copyists, a new genus, called 

 Homoprion, remarking at the same time that the latter was " certainly the fish 

 for which Lacepede established his genus Leiostomus. " Notwithstanding this 

 statement, he has retained the name of Leiostomus for the Leiostomus humeralis 

 of Cuvier and Valenciennes, or Leiostomus obliquus of the Americans, thus assign- 

 ing Lacepede's name and authority to a genus with which that naturalist must 

 have consequently been believed to be unacquainted. The genus thus re- 

 stricted was characterized by the " preopercle smooth or without serratures ; 

 intermaxillary teeth minute ; posterior pharyngeal teeth paved." The Homo- 

 priontes, on the other hand, had " small, villiform, card-like teeth in both jaws ; 

 upper jaw with an external row of larger, conical and pointed teeth ; pharyn- 

 geal teeth not paved ; preopercle with large radiating serratures or spines at 

 its angle. 



We now revert to the description of the Leiostomus xanthurus given by Lace- 

 pede. That description may be divided into two portions : one relates to form 

 and external anatomical or permanent characters ; the other to color, which is 

 evanescent and liable to alteration. 



The zoological characters are as follows, the order being regulated by their 

 respective value : 



1st. Les machoires denuees de dents, et entierment cachees sous les levres. 



2c?. Point de dentelure ni de piquants aux opercules. 



3d. Le bout du museau est mousse. 



4th. La caudale echancree en croissant. 



5th. Dix rayons a la premiere nageoire du dos. 



In all of these respects, the species of Lacepede agrees with Leiostomus ob- 

 liquus of the American naturalists, and not with the one named by Cuvier 

 and his followers Leiostomus or Homoprion xanthurus. That species has 



1st. Well developed teeth on both jaws. 



2c?. "Large radiating serratures or spines" at the angle of the preoper- 

 culum. 



3&?. The muzzle scarcely blunt. 



4th. The caudal fin " entire or slightly longest in the middle." 



5th. Eleven spines supporting the first dorsal fin. 



The Leiostomus obliquus agrees then with the species described by Lacepede 

 in all the anatomical peculiarities mentioned,* and by the same characters is 

 the Leiostomus xanthurus of Cuvier distinguished from it. 



What then are the reason that have induced almost all naturalists to refer 

 Lacepede's description to the latter fish ? 



In the first place, the color may be urged as a reason. 



* Lacepede mentions that his species has often only about a decimetre in length, and 

 then its greatest height is nearly four centimetres. The proportions so indicated also best 

 correspond with the Leiostomus obliquus. 



[April, 



