Fishes of the Western North Atlantic 435 



vance of dorsal; and a dark median streak behind it; margin of mandible and usually 

 the snout behind premaxillary with a dark crossline; base of caudal with a dark 

 crossline; base of anal with a row of dark dots; upper rays of pectoral with dusky 

 points. 



Size. This is one of the smaller of the excessively compressed herrings. The largest 

 among the Study Material is 145 mm (5.7 in.) TL, 123 mm SL, which may be near 

 the maximum. 



Development. The body increases greatly in depth with age and growth, as in many 

 other herrings. The depth in the smallest five examples at hand, 23—38 mm SL, is 

 contained 4.1—4.7 in SL whereas this proportion in the five largest is 3.5-3.6. Fur- 

 thermore, the dorsal profile anteriorly is about straight in the small specimens but 

 concave in the large ones. The maxillary, as indicated in the Description, is short in 

 small examples but becomes produced in large adults; in the smaller examples it is 

 broadly rounded posteriorly and reaches under the anterior half of the eye ; at about 

 50 mm SL it is no longer rounded posteriorly and has an oblique margin; as growth 

 proceeds, the lower angle of the oblique margin becomes longer and sharper, and at 

 65 mm SL it is already well produced. However, it is only in large examples, upward 

 of 1 00 mm SL, that the narrow process reaches to, or even slightly beyond, the margin 

 of the opercle. 



Range. Known from the Atlantic coast of Panama, from the Gulf of Venezuela, 

 and from Trinidad. 



Reference : 



Odontognathus compressus Meek and Hildebrand, Field Mus. Publ., ZooL, JJ (i), 1923: 194 (orig. descr. , 

 type local. Col6n, Panama; of. O.mucronatus\ type USNM 79553). 



Genus Neoopisthopterus Hildebrand 1948 



Neoopisthopterus Hildebrand, Smithson. misc. CoU., no (9), 1948: 6; type species by original designation, Odon- 

 tognathus tropicus Hildebrand. 



Characters. Body slender, strongly but not excessively compressed ; ventral outline 

 anteriorly much more strongly convex than dorsal outline. Bony scutes moderately 

 strong with entire (smooth) margin, the chest and abdomen with a sharp keel. Mouth 

 moderately oblique, with slightly projecting lower jaw. Maxillary short (with no in- 

 dication in the rather small specimens that it will become produced in adults, as in 

 Odontognathus), anteriorly overlapping distal end of premaxillary. Teeth small, present 

 on jaws, palatines, pterygoids, and tongue, but missing on vomer. Gill rakers about 

 17—21 on lower limb of first arch. Dorsal fin small, with about 13—16 rays. Anal 

 fin moderately long, with about 39—48 rays, beginning a short distance in advance 

 of origin of dorsal. Pelvic fin wanting. Vertebrae about 46 or 47. 



Remarks. This genus is characterized chiefly by the structure and relative position 

 of the bones in the upper jaw. In Neoopisthopterus the maxillary and premaxillary over- 



28* 



