T?ie Type r/ Exocoetus exiliens {L, Gmel.). It7 



XVIII. — The Type o/Exocoefus exiliens ( L. Gmel.). 

 By Albert Gunther, F.R.S. &c. 



In the collection of Linnean specimens of Fishes, now in the 

 possession of the Linnean ISociety of London, tiiere is a 

 specimen of Exocwtus, sent by Garden to Linnaeus from 

 Carolina at an uncertain date. I have already mentioned it 

 in my list of Linnean specimens in Proc. Linn. Soc. 1899, 

 p. 37, no. 165 ; but I then failed to recognize its importance ; 

 it undoubtedly proves to be the type of (L.) Gmelin's 

 Exocoetus exiliens. 



It is the dried skin of a fish 6 in. long, which had been 

 preserved in the manner of a botanical specimen ; the head 

 has been compressed and crushed; both sides of the skin are 

 preserved, and the vertebral column shows through laro-e 

 vacuities in the skin; the fins are collapsed, with the ex- 

 ception of the pectorals, which are stretched to their full 

 width and glued to a supporting piece of paper. The speci- 

 men is labelled by Garden, No. 25, and in Linne's hand- 

 writing Exoccetus volans. 



It is not necessary to repeat here Gmelin's diagnosis of the 

 fish ; and 1 may at once proceed to supplement it as far as 

 the dilapidated condition of the specimen will allow. 



The length of the head is contained 4| times in the total 

 (without caudal) ; the snout seems to have been rather 

 pointed. The pectoral fin extends nearly to the caudal, and 

 consists of 14 rays on one side, and 15 on the other ; of these 

 the first is simple (33 mm. long), half as long as the second 

 which is branched ; however, on one side, a rudimentary ray 

 (3 or 4 mm. long) can be made out to precede the first ray * ; 

 none of the rays are lamellated in the basal portion as in 

 E. lamellifer. The ventrals are inserted midway between 

 the gill-opening and the root of the caudal, and reach nearly 

 to the base of this fin. The dorsal and anal fins are collapsed, 

 firmly adhering to the skin of the tail, so that it is difficult to 



* Liitken attached considerable taxonomic value to the presence of 

 either one or two simple rays in front of the first branched pectoral ray. 

 If the additional simple ray is of some length and connected with the 

 second simple ray by an interradial membrane, its presence, no doubt 

 forms a specific character. However, I find that in several species, 

 which were supposed to have, and are generally described as having, one 

 simple ray only, there is a rudimentary additional ray present. It is more 

 or less covered by the skiu, attached to the base of the long simple ray, 

 with which in adult individuals it actually coalesces, thus increasing the 

 power of resistance at the spot where it is most wanted for flying. I 

 suppose that in young individuals this ray is much more con>ipicuously 

 distinct. 



