470 MUSEO NACIONAL DE BUENOS AIRES. 



Gaslerooliisma luolanipus Richardson' 



GasterocJiisma melampus Richardson iu Aun. and Mus. of Nat. 

 Hist. XV, p. 346, May. 1845. 



Radii: — B.5; D. 17/-1/10 et vi; A. 2/10 et vi; 

 C:17 iü; P. 20; V. 1/5. 



Píate XXXVII, figs. 1-3, natural size. 



Tliis fisli is mostclosely allied to Noineiis, of wliii-h it possesses 

 many of tlie characters, but its larger moutli, the form of the jaws 

 approaching much more nearly to that of Scomher, the great com- 

 pression of thebody, and al)0ve all, the free pinuules of the dorsal 

 and anal, justify its being placed in a sepárate genus, in accordan- 

 ce with the manner of which the Scomberidae have been hitherto 

 subdivided. 



The profile bears considerable resemblance to that of a common 

 mackerel, and the tail at the base of the caudal is very slender, 

 but has no vestige of a keel. The length of thehead, which equals 

 the height of the body, is contained four times and a half in the 

 total length, and the thickness of the body is less than one-third 

 of its height, the back and belly being both acute. The nape is 

 more broadly rounded, but the top of the head is traversed by a 

 smoot, acute, mesial keel, which is continued to the tip of the 

 uarrow, acute snout. The lower jaw is also acute, and the cleft of 

 the mouth is half the length of the head. The maxillary reaehes 

 rather beyond the raiddle of the eye, and its slender middle part 

 only is covered by the preorbitar when the mouth is closed. The 

 jaw- teetli are finely subulate, acute, slightly ourved, and rather 

 widely set in a single row. The vomerine and palatine teeth are 

 more delicate and not so evenly set. 



The cheek is scaly, and there is a scaly pateh on the supra-sca- 

 jjulars; but the top of the head, jaws, preorbitar, disk of the preo- 

 perculum, and gilí -niembranes are smooth. There are no scales on 

 the gill-covers in the specimen, but as the iutegument clothing 

 these bones is injured, it is possible that thej' may be more or less 

 scaly in the recent fish. The lateral line is moderately arched till 

 it comes opjjosite of the first sepárate pinnule, when it takes a 



' EicHARDsoN. Ann. and Mag. of Nat. Ilist. xv, p. 3l(i. 181,^, y Voy. Erebus and 

 Terror Fishes. p. 60, pl. .xxxvit, fig. 1-3. 



