17. psETTus. 487 



e. Adult. Purchased of M. Parzudaki. 

 /. Adult : stuiFed. Old Collection. 



Skeleton. — The skull is slightly compressed and rather short; a' 

 very high, triangiilar occipital crest extends from "^he occipital joint 

 to the anterior extremity of the frontal bones ; there cU'e two ridges on 

 each side of this crest, the interior proceeding froin the anterior angle 

 of the orbit, the exterior trom the superciliary margin. The max- 

 illary becomes gradually broader posteriorly ; the intermaxillary has 

 the posterior processes of moderate length ; the mandibula with a 

 rudimentary muciferous channel. The praeoperculum has the lower 

 Hmb shorter than the posterior ; both meet at a right angle, which, 

 however, is rounded ; its interior ridge is slightly raised above the 

 level of the bone, and there is a rudimentary muciferous channel 

 behind it. The operculum is twice as high as wide, with a notch 

 superiorly and another posteriorly ; the sub- and interoperculum are 

 nearly of equal length. The infraorbital ring is very narrow, the 

 praeorbital somewhat wider. The suprascapula is suspended to the 

 skull by two processes ; the scapula is oblong ; the humerus, with the 

 ulna, forms a spacious cavity for the pectoral muscles ; there is a 

 wide free space between the two bones. The pubic bones are slender 

 and narrow, similar to those in lAcJiia. 



There are ten abdominal and fourteen caudal vertebrce, the length 

 of the former portion of the vertebral column being to that of the 

 caudal as 1 : 1-9. The abdominal vertebrae are very compressed in 

 their longitudinal diameter, especially the anterior ones. The neural 

 spines are strong, erect; those of the abdominal vertebrae are close 

 together, and being dilated, they leave scarcely any interspace be- 

 tween them. There are three si)urious interneural spines, each of 

 which is provided superiorly with a point directed forwards. The 

 interneurals are closely fixed together, and form, as it were, one un- 

 interrupted solid plate. The haemals are strong, and the anterior 

 ones very elongate ; the first is firmly joined to its interha^mal, both 

 forming an exceedingly strong bone, which is longer than the whole 

 vertebral column ; its inferior part is dilated, and provided with two 

 ridges, radiating from the base of the first anal spine. Although we 

 have observed the same structure in aU the preceding Carangidce, I 

 know no other instance in which those bones are developed to an 

 equal extout. The second, third, fourth and fifth haemal spines are 

 dilated into transparent lamellae closing the interspaces between the 

 spines. The interhaemals are joined together like the interneurals. 



2. Psettus argenteus. 



Chaetodon argenteus, L. Amccn. Acad. iv. p. 249 : Bl. Schn. p. 230. 



Scomber rhombeus, Forsk. p. 58. 



Centrogaster rhombeus, L. Gm. p. ISbS. 



Acantbopus argenteus, Lacep. iv. pp. 558, 559. 



Centropodus rliomboidalis, Laccj). iii. pp. 30.3-305 



Russell, pi. 59. 



Psettus rhombeus, Chiv. ^' Val. a ii. p. 245 ; Cuv. lleqne Anim. Ill Poiss. 



