48 Prof. Peters on a new Species of Leptocephalus. larval form of the Congroid Nettastoma melanura *. The resem-blance between those two forms will be readily appreciated by reference to Dr. Kaup's figures of the two. Perhaps the affinities of those Leptocephali with an expanded caudal are to be sought for elsewhere. As to Esunculus Costai, it resembles the young of a Clupeoid ; but the high insertion of the pectoral fins, if existent in nature, forbids for the present its positive identification with such. Stomiasunculus resembles^ in general features, a less ad-vanced larval Clupeoid, about three days oldf, in which the ventral fins have not yet appeared. Suspicion, however, may be entertained that it may perhaps be the young of some other type (possibly Stomiadoids), on account of the backward position of the dorsal fin. I have myself, in company with a friend, seen the young of Clupeoids, which would have either been referred to Esunculus or considered as the type of a closely allied new genus, on account of the inferior insertion of the pectoral fins ; and so transparent were they, that their eyes alone indicated their position in the water. Although entertaining no doubts concerning the larval nature of Esunculus and Stomiasunculus, I only venture to suggest the possible relations with much reserve. As to Porohronchus, KaupJ, it is, perhaps, related to Fierasfer; but the character of the first elongated dorsal ray requires to be known before a decision can be arrived at. VIII. — Description of a new Species of Leptocephalus. By Professor Peters §. Leptocephalus {Diaphanichthys) brevicaudus, Peters. Body very much compressed ; profile of the ventral margin convex, of the back nearly straight. Snout very acute, convex before the eye, a little shorter than the diameter of the eye ; mouth cleft as far as beneath the middle of the eye, armed on each side, both above and below, with eight straight acute teeth, behind which, in the upper jaw, are some smaller acute teeth. The posterior nasal apertures are situated on the muzzle, rather nearer to the eyes than to the apex. The eyes are placed in the middle of the head. Branchial clefts very narrow. No pectoral, dorsal, or anal fins, the extremity of the body only being sur-rounded by the caudal fin, which extends above and below for * Raf. Caratteri, &c. (1810) p. 66, tav. 16. f. 1. t See Sundeval, " Om Fisk5Tigels Utveckling," in Kongl. Vet. Akad. Hand. i. (1855) tab. 4. fig. 6. X Ann. & Mag. Nat. Hist. ser. 3. vi. (1860) p. 272. § Translated by W. S. Dallas, F.L.S., from the ' Monatsber. Berk Akad. der Wiss.' June 1864, p. 399.
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