17. PSETTTJS. 487 



e. Adult. Piu'chased of M. Parzudaki. 



/. Adult: stuffed. Old Collection. 



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

 very high, triangular occipital crest extends from the occipital joint 

 to the anterior extremity of the frontal bones ; there are two ridges on 

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

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

 illary becomes gradually broader posteriorly ; the intermaxiUaiy has 

 the posterior processes of moderate length ; the mandibula with a 

 rudimentary muciferous channel. The prseoperculum has the lower 

 limb 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 interoperculiun are 

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

 jDrajorbital somewhat wider. The suprascapula is siispended to the 

 skull by two j^rocesses ; 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 Lichia. 



There are ten abdominal and foiu'teen 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 dQated, they leave scarcely any interspace be- 

 tween them. There are three spurious interneural spines, each of 

 which is provided superiorly with a point dii-ected forwards. The 

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

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

 ones very elongate ; the first is firmly joined to its interhaimal, 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 structiu^e in all the preceding Carcoifjidce, I 

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

 equal extent. The second, third, fourth and fifth h^mal spines are 

 dilated into transparent lamellae closing the interspaces between the 

 spines. The interhaemals are joined together like the internenrals. 



2. Psettus argenteus. 



Chsetodon argenteus, L. Amccii. Acad. iv. p. 249 ; £1. Si'Jui. p. 230. 



Scomber rhombeus, Forsk. p. 58. 



C'entrogaster rhombeus, L. Gm. p. 1338. 



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



Centropodus rhomboidalis, Lacep.'in. pp. 303-305. 



Rmsell, pi. 59. 



Psettus rhombeus, Cuv. H,- Val. vii. p. 245 ; Cuv. E<\f/)ie Anim. III. Pom. 



