342 riUSTIl'OMATID.'U. 



the head ; the second of the anal three-fourths of the second of the 

 dorsal. Silvery ; dorsal with a blackish margin. 

 Atlantic coasts of Tropical America. 



a. Fine specimen. Cuba. Presented by the Zoological Society. 

 b-f. Adult and half-grown : skins. Jamaica. From Dr. Pamell's 



Collection, 

 r/. Adult : not good state. Puerto Capollo. Purchased of Mr. Brandt. 

 h. Adult : not good state. South America. Purchasedof Mr. Brandt. 

 i-I. Adult: not good state. South America. Purchased of Mr. Brandt. 

 VI. Half-grown. South America. Presented by Sir K. Schomburgk. 

 n. Adult : skeleton. From the Haslar Collection. 

 0. Adult : skeleton. From the Collection of the Zoological Society. 

 2>. Half- grown. From the Haslar Collection. 

 (/. Young. 



SJceleton. — I have had skeletons of the fish prepared with two 

 anal spines as well as with three, and having found them exactly 

 alike, I am fully coavincec^ that the form with two anal spines is 

 merely accidental in so.ne individuals, and that O, rhombens of Cmier 

 must be considered as a nominal species. I have, however, preferred 

 the name of G, rliomheus to that of G. brasiliensis. 



The skeleton differs from that of G. plumieri in several points. 

 The maxillary bone is very irregularly shaped, and exhibits a thick 

 protuberance in the middle of its outer surface ; this is, however, 

 more conspicuous in very old specimens. The interna axillaries and 

 the mandibula arc very much like those of G. pJumieri. The prae- 

 orbital has the maxillary margin concave and entire ; its posterior 

 j)art is rather broader than the remainder of the infraorbital arch. 

 The head of the vomer is rather flat, without a distinct i:)rominence ; 

 the palatine bones exhibit a slight groove. Both the margins of the 

 prieoperculum are straight ; the angle is rounded, and Like the inferior 

 limb armed with a very distinct and equal serrature ; the posterior 

 limb is entire. The remainder of the opercidar apparatus as in 

 G. plumicri. The occipital crest extends fui'ther forwards than in 

 G. plumieri, the anterior groove being situated above the anterior 

 portion of the frontal bones ; there is, besides, this peculiarity in 

 G. rhombcKS, that the groove mentioned communicates with the 

 orbital cavity by a pair of large oval holes. 



There are nine abdominal and fifteen caudal vertebra'. ; the length 

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

 caudal as 1 : 1-8. The ribs are rather feeble, \\dth a posterior and 

 anterior longitudinal groove ; the first three libs arc very slender, 

 short, and without a prominent knob. The neural sjunes become 

 gradually longer to the thirteenth vertebra, and are furnished with a 

 more or less distinct, flat, transparent, posterior ridge. The inter- 

 neural spines do not differ from those of G. plumicri, except that of 

 the second dorsal spine, which, like that spine itself, is not quite so 

 strong. The first intcrhtemal is exceedingly strong, and has in front 

 a very broad and cmai-ginate ridge ; its length equals that of the 

 first nine vertebrae. 



