120 Mr. C. T. Regan 07i the 



liavc not hitherto been understood to belong to it suggests the 

 need of a, complete revision. 



The family as now defined includes the Nomeidaj of 

 Giinther, minus the genus Gastrochisma ; the latter resembles 

 Nomeus only in its long ventral fins, depressible into a deep 

 furrow. But as in all the Scombridaj and Carangidaj, as 

 well as the Strom ateidaj, the ventrals are inserted close 

 together, more or less widely attached to the abdomen by 

 membrane, and folding back close together into a more or less 

 well-marked groove or hollow, the extreme development of tiiis 

 leature cannot by itself be taken as evidence of genetic affinity. 

 In all other characters Gastrochisma \i a tyjncal member of 

 the Scombrida3 and must be placed in that family. The 

 single species, Gastrochisma melampuSj closely resembles in 

 appearance Lepidothynnus llattonii, Gthr.*; and as the 

 correspondence extends to the number of scales, fin-rays, and 

 vertebra3, I have not the least doubt that the latter is only 

 a large example of the former species. The smaller size of 

 the ventrals in the laiger fish is paralleled in the genera 

 Nomeus, Psenes, Lirus, &c. As in other Scombridge, the ribs 

 are inserted at the ventral ends of the ha3mapophyses, and it 

 is not impossible that the skeleton of Lepidothynnus, described 

 from a photograph, may have been incorrectly set up, as it 

 shows the ribs inserted near the bases of the litemapophyses. 

 In its compressed body and short gill-rakers Gastrochisma 

 resembles Cyhium, with which it also agrees in the structure 

 of the dorsal fin and the number of vertebrae, whilst the high 

 occipital crest is similar to that of Coryphcena. 



It has been generally supposed that the teeth in the 

 oesophagus are borne by gill-rakers of the last branchial arch, 

 and throughout the family there are short processes which 

 may be of this nature ; but, in addition, the anterior part of 

 the a3so])hagus has on each side a large muscular sac, which 

 is studded with numerous separate conical or papilliform 

 processes bearing setiform teeth similar to those which occur 

 on the gill-rakers and pharyngeals. In Stromateus, Peprilus^ 

 and Stromateoides these lateral sacs are sim})le and rather 

 elongate; in the other genera they are much shorter and 

 broken up by longitudinal folds into several compartments on 

 each side. 



Synopsis of the Gtnera. 



I. Ventral fins present in the adult ; oesophagus 

 with longitudinal plications. 

 A. Lateral line concurrent with dorsal profile. 



* Giinther, ' Challenger ' Pelagic P'ishes, p, 15, pi. vi. 



