94 Transactions. — Zoology. 



are exemplified by several other varieties of fishes ; but the 

 vessels' disturbance of them in the water, especially if a 

 steamboat, is frequently, I think, a cause of their misdirection 

 of flight. 



Order PHYSOSTOMI. 



Fam. SCOMBRESOCID^. 



Genus Exoccetus. 



Third division, ventral fins long, extending beyond posterior 

 termination of base of anal. 



Exoccetus ilma, sp. nov. 



D., 12; P., 16; V., 6; A., 12; C. (7 upper limb, 8 lower 

 hmb), 15. 



B., 8. L.L., 28 scales to origin of ventrals ; 25 from same 

 to termination of line which finishes before caudal is reached ; 

 29 scales between occiput and origin of dorsal ; and 6 longi- 

 tudinal series of scales between origin of dorsal and lateral 

 line. (This is common also with three other species of 

 Exocoetus.) Speculiger also has same number, occiput to 

 origin of dorsal, but according to Giinther 6 to 7 between 

 each point and lateral line. 



Height of body is contained six and seven-tenths times 

 in the total length (without caudal) — viz., if such length is 

 reckoned along the median line from tip of snout to termi- 

 nation of the fish at the base of the central caudal rays — but if 

 such height is compared with the total distance from snout to 

 the vertical of origin of rudimentary rays of caudal, then it is 

 contained in the latter six and a quarter times. This height 

 of body is greatest and equal in that space between the 

 verticals from a little posterior to the origin of pectorals and at 

 the origin of ventrals. 



Giinther's description of speculiger gives one-sixth or 

 nearly one-seventh of the total length (without caudal) as the 

 proportion of depth, and in nigripinnis one-sixth or a little 

 less than one-sixth total length (without caudal). Pour other 

 species in this division of Exocmtus are described with the 

 same proportion as one-sixth, and four of it as a sixth and 

 a half, which broadly means that about such a proportion 

 appertains to the Exocceti with long ventral fins. 



The length of the head is contained five and a half times in 

 the total length (without caudal) first defined — i.e., a proportion 

 of two-elevenths. Giinther's descriptions of speculiger and 

 nigripinnis give head as two-ninths. The snout is very obtuse 

 and short ; on Plate VI. its peculiarities are reproduced. 

 In its profile it is abrupt ; the lower jaw projects beyond the 

 upper when mouth is closed ; therefore the chin forms the 



