CATALOG OF THE FOSSIL FISHES IN THE CARNEGIE MUSEUM. 



415 



An interesting structure not hitherto observed in connection with this species 

 ^is the presence of a long and tapering air-bladder, the calcified walls of which show 

 a series of transverse ridges not unlike those formed by muscle-fibres in modern Ga- 

 noids and Dipnoi. Confluent with the intestinal tract in front, the organ in question 

 extends longitudinally close to the ventral body-wall along one side of the sup- 

 ports for the anal fin, and terminates in a closed sac immediately behind the latter. 



Fig. 5. Hypsocormus insignis Wagner. 



(After A. S. Woodward, Cat. Foss. Fishes Brit. Mus., Pt. Ill, 

 fig. 40, p. 393.) 



Somewhat similar structures have been observed in Pachycormus and Astheno- 

 cormus, and are interpreted in the latter by B. Vetter as spiral valves of the intestine 

 (c/. infra, p. 461). The numerous internal septa ("convolutions" of Vetter), 

 small size of the organ, and its prolongation into the region posterior to the anal 

 fin, are characters which militate against this view of its nature. For the sug- 

 gestion that the structure in question is a calcified air-bladder the writer is indebted 

 to his friend, Dr. C. H. Eigenmann, than whom no one is better qualified to pass 

 judgment upon the actual specimens submitted for examination. 



According to this eminent authority, the form and position of the air-bladder 

 exhibit a wide range of variation among closely related genera of modern teleosts, 

 even within the limits of a single subfamily, such as the Curimatinse" of the Chara- 

 cidae or Sternopyginae" among the Gymnotidse. 



'" Eigenmann, Carl H. and R. S., "A Revision of the Edentulous Genera of Curimatinse," Annals 

 N. Y. Acad. Sci., 1889, Vol. IV, pp. 409-440. 



"Ellis, Max Mapes, "The Gymnotid Eels of Tropical America," Mem. Carn. Mus., Vol. VI, 

 No. 3, 1913, pp. 186-189. 



