ROOM V. AIR-BLADDER OF MACROPOMA. 437 



large, rounded, and fan-shaped, with strong equal rays, sup- 

 ported by the inferior and superior spinous processes of the 

 caudal vertebra. 



A ir-bladder (or stomach ?) of the Macropoma. In every 

 example of this fossil fish that I have dissected, there lies 

 within the body, generally nearest the upper or dorsal part of 

 the cavity, a long, hollow, cylindrical substance, often seven 

 inches in length, and 1J inch in diameter, covered with a 

 thin, brittle, scaly integument, which readily separates into 

 two or three laminse. The anterior part of this organ, which 

 lies close to the posterior margin of the opercular bone, is 

 always imperfect, appearing as if torn or ruptured ; the caudal 

 extremity terminates in a cul-de-sac. From the situation 

 and structure of this viscus, I supposed it to be an air-bladder, 

 and described it as such in the " Fossils of the South Downs," 

 (in 1822); but on M. Agassiz's visit to my Museum at 

 Brighton, that eminent naturalist pronounced it to be the 

 stomach. Recent microscopic investigations of the investing 

 integument, have, however, tended to establish the correct- 

 ness of my original interpretation of the nature of this 

 remarkable body. 1 



The Macropoma when at maturity, was between two and 

 three feet in length ; its massive skeleton indicates a powerful 

 frame, and its thick scales, strong fins, and sharp teeth, prove 

 that it was a voracious fish, capable of overtaking and seizing 

 live prey. I would especially direct attention to the various 

 states of distension in which the air-bladder appears in the 

 specimens here displayed. 



1 My youngest son, Mr. Eeginald Han tell, first detected the intimate 

 structure of this organ, which has recently been admirably investigated 

 by Prof. Williamson. See an able memoir On the microscopic structure 

 of the scales and dermal teeth of some ganoid and placoid fishes. By 

 W. C. Williamson, Esq. " Philos. Trans." 1849, p. 435. PI. XL1II., figs. 

 27, 28, represent the microscopic structure of the scales of the Macro- 

 poma : and figs. 29, 30, of the air-bladder, described at pp. 462 465. 

 Professor Williamson observes in relation to this fossil viscus" I am 

 disposed to believe it to have been an organ fulfilling the functions of 

 an air-bladder. Its osseous structure would render it capable of resisting 

 a considerable amount of pressure, and if its patulous extremity were 

 closed up by an elastic valvular membranous appendage, the fish might 

 have regulated its buoyancy by increasing or diminishing the compres- 

 sion of the gaseous contents of the bladder, and thus facilitate its 

 movements in either shallow water or at great depths in the sea. 





