34 



FOSSIL MEDUSA. 



area is outlined at the margin by dark material which is similar to that of 

 the radial canals, but which does not extend over the central parts. It is 

 not possible to distinguish any canals that might be referred to the oral 

 arms. The number of canals is from 30 to 34, and exceeds that of any 



of the silicified specimens. Fig. 8 of PI. VIII has 20 

 lobes indicated, and there may have been attached 

 to the central axis others that are now concealed. 



The interior canal system of the simple complex 

 form of this species is shown by the transverse hori- 

 zontal sections illustrated in fig. 3a of PI. XVII and 

 fig. 7 of PI. XXIII. It is unfortunate that we have 



Fig. 8. — Laotira Cambria. Dia- , -. . l • i • 1 



grammatic vertical section of the no good vertical sections snowing the entire canal 



specimen represented by tigs. 4, 4a, . -i 1 e l n 



and 4b of PI. XVIII. The general System 111 tile lUOre COllipleX tOmiS, SUCh as are fig- 

 form only is taken from the specimen. 

 The interior canals are restored from 

 sections of other specimens, snch as 

 those represented by figs. 1, 3, and 4 

 of PI. XXIII. 



a, exumbrella lobes with radial 

 canals ; A-, axial or pillar canals ; o, up- 

 turned oral anus with interior canals ; 

 2", central axis; </, central stomach; 

 h, buccal stomach. 



ured on Pis. XII and XIV. There is sufficient, how- 

 ever, in fig. 5 of Pi. XII and fig. 3 of PI. XIV, and 

 many similar specimens, to prove the existence of a 

 canal in each one of the lobes of the exumbrella and 

 in the free lobes of the subumbrella, and frequently 

 in the inosculating lobes of the subumbrella. 

 One of the simplest types is represented by text fig. 8, in which the 

 canals of the exumbrella radiate from the center and there is a simple axis 

 connecting with the radiating oral arms beneath. 



In a more complex individual, in which the central axis seems to have 

 disappeared and only the transverse canal 

 of the subumbrella lobe is present, the 

 gastro- vascular system appears to be rep- 

 resented by canals in the subumbrella 

 oral arms or lobes and by the canal sys- 

 tem extending through the exumbrella 

 lobe or lobes. This is shown diagram- 

 matically by text fig. 9. 



A still more complex canal system is 

 hvpothetically shown by text fig. 10. In this there is the broad exumbrella 

 surface with its canal system and the oral or subumbrella lobes showing the 

 combination of characteristics found in text figs. 8 and 9. Text fig. 10 is, in 

 fact, a transverse vertical section of three or four individuals united by the 

 exumbrella surface. 



Fig. 9. — Laotira cambria. Transverse section of a 

 complex specimen of the type of figs. 3, 3a. 5, and 5a 

 uf PL XIII. 



«, upper or exumbrella lobes; o, oral arms with 

 interior canal; g, interior canal corresponding to the 

 upper central stomach in Brooksella and the simple 

 form of Laotira. 



