356 



Mr. C. T. Regan on the Caudal Fin 



Leptohpis seems to have been exactly like Elops, but in 

 some species of Thrissops a series of no less than six separate 

 uron enrols can bo peon. 



The caudal fin skeleton of the Clupeidse, which has recently 

 boon described and figured by Mr. R. H. Whitehouse (Proc. 

 Roy. Soc. B. Ixxxii. p. 139), differs from that of the Elopidas 

 in that the last two centra have aborted, and the anterior 

 uroneural is ankylosed with tlie actual last centrum (corre- 

 sponding- to the third last of the'Elopidse). 



As the Clupeidas appear to be the most generalized Teleo- 

 steans examined by Mr. Whitehouse, I may mention the 



Fig. 2. 



Epaxial rays, with proximal portions of one or two upper hypaxial rays, 

 of caudal fins of Megalops. 



a. J\T. cyprinoides, from a specimen of 320 mm. 



b. M. atlanticus, from a specimen of 1800 mm. 



Albulida?, Alepocephalidse, Salmonidae, Osteoglossidse, Eso- 

 cida?, Umbridse, and Aulopidae as agreeing with the Elopida? in 

 having upturned centra, and in the persistence of the anterior 

 uroneural as a distinct bone. 



The Elopidse show some features of irterest in the arrange- 

 ment of the caudal tin-rays, for, as will be seen from the 

 accompanying figures, both species of. Megalops resemble the 

 Oligopleuridai in that the epaxial rays are divided into an 

 anterior and a posterior series, the former supported by neural 

 spines and basalia, the latter inserted on the uppermost 

 hypaxial ray. These epaxial rays appear to be usually more 



