OCYSTIAS 19 



Vertebrae 21 -j- 21 = 42, the anterior hour-glass shaped, as deep as 

 long, the posterior larger and more elongate, sharply grooved. 



Dorsal fins separate, the first beginning behind base of pectoral, of 

 about 22 very slender spines, rather wide-set, the anterior highest, 2^ in 

 depth of body. Soft dorsal low, of 16 or more slender rays, anal similar, 

 beginning just behind front of first dorsal. The number of rays not 

 certain. No trace of finlets; pectorals rather broad, of 15 or more rays, 

 broken; ventrals obliterated. Caudal rather large, wide forked, the 

 equal lobes about 5 in body; neural and haemal spines rather strong, 

 especially mesially; the last few vertebrae with but traces, indicating a 

 very slender caudal peduncle. Interneurals all short and small, shorter 

 than the dorsal spines and rays, interhaemals also very small and slender, 

 shorter than the rays, about five times in depth of body at that point, 

 very oblique, contrasting sharply with the strong, long, parallel inter- 

 haemals of THYRSOCLES ; ribs slender, very oblique. 



With much resemblance to the associated THYRSOCLES and THYRSION, 

 the present species is sharply distinguished by the very short and weak 

 interhaemals and interneurals, by the many-rayed first dorsal fin and by 

 the relatively short tail. From TURIO, which has also weak interneurals, 

 it is separated by the more numerous and shorter vertebrae; it is the 

 most slender species of the mackerel family yet known. For this species 

 is proposed the name of OCYSTIAS SAGITTA (oxvoTog, swiftest). 



Thyrsocles Jordan and Gilbert, new genus. 

 (Type: THYRSITES KRIEGERI Jordan and Gilbert (1919). 



Large mackerels with the body rather elongate, the depth about 4% 

 in body, the vertebrae about 22 -j- 25 = 46 in number, quadrate in form, 

 little constricted, each about as deep as long, each conspicuously three- 

 ridged. Head large, the opercle moderate, occupying less than half post- 

 orbital part of head ; mouth large, with small, compressed, wide-set teeth 

 so far as ascertainable. First dorsal weak, of 10 to 20 slender spines, 

 not much elevated. Interhaemal bones unusually long, parallel, the an- 

 terior curved, the others straight, forming a conspicuous grate-like struc- 

 ture, these bones extending two-thirds the distance to the back bone, and 

 more than one-third depth of body at insertion of anal, which is well 

 behind front of soft dorsal. 



This genus may be regarded as an ally of SCOMBEROMQRUS, having 

 similar vertebrae and interhaemals, but the anal farther back, and the 

 teeth smaller and apparently much more numerous. The number of 

 dorsal spines is uncertain. In SCOMBEROMORUS (MACULATUS, CAVALLA, 

 COMMERSONI examined) the interhaemals are strong and parallel, much as 



