Dr. W. G. Ridewood on Fly rug -fishes. 545 



claim to the title "flying-fish" than the others, for there is 

 no doubt in their case that the pectoral fins are flapped 

 vigorously during the passage of the fish through the air. 

 The various species of Gastropelecus possess a deep, laterally 

 compressed body, with fairly long and curved, but not 

 remarkably large, pectoral fins. The length of the fish is 

 some 3 inches or less. The habits of these fishes are alluded 

 to in Mr. and Mrs. Beebe's book 'Our Search for a 

 Wilderness ' (London, 1910), and the species and their habits 

 are described by C. II. Eigenmann (" Freshwater Fishes of 

 British Guiana/'' Memoirs of the Carnegie Museum, v., 

 Pittsburg, 1912, p. 47). The fishes are said to dart forward 

 for a distance of 40 feet or more, beating the water with 

 their pectoral fins, the upper part of the body alone being 

 exposed, and the sharp keel of the breast acting as a cut- 

 water. They then leave the water entirely for a distance of 



5 or 10 feet, and, when exhausted, fall sideways into the 

 water again. 



Removal of the skin from the front half of the body 

 displays the great pectoral muscle, which is one of the most 

 striking features of the fish. This muscle is in the form of 

 a thick sheet, thinning off at the front and lower edges. 

 The muscle-fibres radiate in an upward direction from the 

 front and lower edges to the base of the pectoral fin, to the 

 underside of the fin-rays of which their tendinous extre- 

 mities are attached. This great muscle, by its contraction, 

 draws down the fin. The elevator muscles of the fin are 

 small, no larger than would be the case in an ordinary fish 

 of the same size. 



The great external pectoral muscle arises from the whole 

 of the side of a large keel or plate of bone lying in the 

 median plane of the body ; the plate is corrugated in a 

 radiating manner, like a half-opened fan (see Plate XVI.), 

 the radiating ridges of one side corresponding with the 

 radiating grooves of the other side. This corrugation of the 

 lamina of bone affords greater strength, and offers a larger 

 surface for the attachment of the muscle, than would be the 

 case if it were fiat. The front edge of the keel reaches the 

 surface of the body, and is covered by thin skin only ; it 

 forms the edge of the et cut- water." The pectoral girdle of 

 Gastropelecus has already been figured by C. T. Regan (Ann. 



6 Mag. Nat. Hist. (8) viii., July 191*1, p. 19), but when 

 dissociated from the rest of the skeleton its relatively great 

 size is not apparent (see Plate XVI.). 



The great keel is composed of the coalesced right and left 

 coracoid (hypocoracoid) bones ; the upper front point of it 



