432 Memoir Sears Foundation for Marine Research 



Head small, Its length 5.25-5.7 in SL, its depth at vertical from slight cross- 

 groove at occiput 5.9-6.65. Snout a little shorter than eye, 3.75—4.05 in head. Eye 

 3.5—3.55. Interorbital very narrow, 10-11.5 in head. Cheek, about as long as deep. 

 Mouth nearly vertical. Maxillary produced into a long narrow process reaching 

 margin of opercle in larger one, 1.25— 1.3 in head. Mandible projecting strongly, its 

 tip a little below dorsal outline, its margin within mouth rising strongly, forming a 

 broadly rounded obtuse angle, 2.1—2.2 in head. Gill rakers fairly strong, only about 

 half of length of eye, their inner margin rather strongly serrate, 24 or 25 on lower limb 

 of first arch. Teeth all small to minute, in a single series on mandible, premaxillary, and 

 maxillary; missing on membranous section between the last mentioned elements; minute 

 teeth on palatines and pterygoids, but none on vomer; an elongated patch on tongue. 



Dorsal fin small, feebly developed (damaged specimens at hand), its origin not- 

 ably more than length of head behind origin of anal, about twice as far from the 

 posterior margin of eye as from base of caudal, its distance from margin of snout 

 1.35— 1.45 in SL. Caudal fin damaged, the lower lobe evidently the longer. Anal fin 

 very long, its origin nearer to tip of mandible than to base of caudal by about twice 

 diameter of eye, its base 1.8— 1.9 in SL. Pectoral moderately large, a little longer 

 than head, reaching 4th or 5th from last ventral scute, 4.55—5.25 in SL. 



Color. Large preserved specimens pale; sides of head silvery. A pale lateral band 

 (no doubt silvery in life), very narrow (a mere line), anteriorly, becoming fully half as 

 broad as eye over posterior half of anal. Back with dusky punctulations extending for- 

 ward onto head and snout and onto tip of mandible ; punctulations also on fins. 



Relationship. Compared to O. compressus, the body of O. mucronatus is more slender 

 and apparently less compressed, the anal fin is longer, and the dorsal fin is more pos- 

 teriorly placed. And in all these respects mucronatus is nearer to the Pacific panamensis 

 than to compressus \ however, it is even more slender than panamensis, and its gill rakers 

 and anal rays are more numerous. If the interruption in the series of ventral scutes 

 below the pectorals (p. 431) were normal, which seems doubtful, this would con- 

 stitute another important difference that separates mucronatus from the other species of 

 the genus. However, a slight concavity in the ventral outline has been noticed in a large 

 specimen of O. panamensis and in a much smaller specimen of O. tropicus from northern 

 Peru, recently referred to a new genus; however, in each instance the scutes are 

 fully developed in the concavity. Other specimens of the same species have no such 

 concavity in the ventral outline, nor do any of the numerous specimens of O. compressus 

 examined. Furthermore, this question of abnormality is not answered in Norman's 

 revision {gg: 15), wherein he gave no information other than "Ventral scutes 8 + 12," 

 which is in approximate agreement with the number of scutes before and after the 

 interruption at the concavity on the specimens at hand. It may be significant, however, 

 that in the description of O. panamensis in his revision, the number of ventral scutes is 

 also written "13 + 16"; there certainly is no interruption in the series of scutes in the 

 specimen of that species before me. 



Range. Known from the coast of Guiana and from Trinidad (Port-of-Spain). 



