290 



U. S. P. E. K EXP. AND SURVEYS ZOOLOGY GENERAL REPORT. 



A large species: the largest hitherto known of this genus. It is twelve inches in total length, 

 the head forming somewhat less than the fourth of it. The greatest depth is nearly equal to 

 the length of the head. The eye is sub-circular, and its diameter contained about six times, or 

 a little more, in the length of the side of the head. The dorsal and anal fins are sub-trapezoid, 

 the anal being smaller than the dorsal. The origin of the ventrals is situated but slightly in 

 advance of the dorsal fin. The latter is higher than long : a character of the genus. The pec 

 torals and ventrals are of moderate development. 



D 1, 8, or 1, 9 + 1 ; A 2, 8 -f 1 ; C 8, 1, 9, 8, 1, 7 ; V 1, 10 ; P 18. 



The scales are quite large, deeper than long upon the anterior portion of the body, and longer 

 than deep upon the posterior portion, with numerous radiating grooves upon their posterior 

 section only. The lateral line is somewhat deflexed on the middle of the flanks and nearer the 

 insertion of the ventrals than the base of the dorsal. 



The dorsal region is bluish grey ; the sides and belly are silvery white, sometimes golden, 

 but always in contrast with the tint of the back. 



List of specimens. 



3. TIGOMA OBESA, Grd. 



SPEC. CHAR. Body short and compact ; peduncle of the tail rather attenuated. Head small, constituting the fifth of the 

 total length. Snout abbreviated and rounded ; posterior extremity of maxillar bone extending to a vertical line drawn in front 

 of the orbit. Eye moderate sized, sub-circular; its diameter entering a litt e over four times in the length of the side of the head. 

 Anterior margin of dorsal fin nearly equidistant between the extremity of the snout and the fork of the caudal fin. Origin of 

 ventrals somewhat nearer the insertion of the caudal than the extremity of the snout. Bluish grey above ; yellowish white 

 beneath, with a lateral reddish streak. 



SYN. Tigoma obesa, GRD. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 206. 



A very characteristic species, owing to its short and deep body, its short and conical head, and 

 its small fins. It bears a general resemblance to T. purpurea, but its head is much smaller. 

 The anal fin is somewhat larger than the dorsal, both of them are sub-trapezoid in shape. The 

 extremities of the ventrals are far from reaching the vent ; the same is true of the pectorals with 

 reference to the origin of the ventrals. The following formula gives the number of the rays : 

 D 1, 8 + 1 ; A 2, 9 + 1 ; C 6, 1, 9, 8, 1, 5 ; V 1, 8 ; P 15. 



The scales are moderately developed, presenting the same variations in length and depth, 

 according to the regions of the body where they occur, as in T. Ucolor. The lateral line is 

 nearly median, being but slightly deflexed and but slightly nearer the insertion of the ventrals 

 than the base of the dorsal. 



The upper region is bluish grey, whilst the inferior region is yellowish white. A reddish 

 streak may be observed above the lateral line from the opercular apparatus to the tail. The 

 vertical fins are greyish yellow ; the pectorals and ventrals exhibiting a rather more yellowish 

 tint. 



