34 
FOSSIL MEDUS 4. 
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. 
tas 
not possible to distinguish any catials that might be referred to the oral 
arms. The number of 
Fia. Dia- 
8.—Laotira cambria. 
grammatic vertical section of the 
specimen represented by figs. 4, 4a, 
and 4bof Pl. XVIII. The general 
form only is taken from the specimen. 
The interior canals are restored from 
sections of other specimens, such as 
those represented by figs. 1, 3, and 4 
of Pl. XXIII. 
a, exumbrella lobes with radial 
canals; k, axial or pillar canals; 0, up- 
turned oral arms with interior canals; 
a, central axis; g, central stomach; 
h, buceal stomach. 
canals is from 30 to 34, and exceeds that of any 
of the silicified specimens. Fig. 8 of Pl. VITT 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 Pl. XVII and 
fig. 7 of Pl. XXIII. 
no good vertical sections showing the entire canal 
It is unfortunate that we have 
system in the more complex forms, such as are fig- 
ured on Pls. XII and XIV. There is sufficient, how- 
ever, in fig. 5 of Pl. XII and fig. 3 of Pl. 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 
oral arms or lobes and by the canal sys- 
tem extending through the exumbrella 
This is 
matically by text fig. 9. 
lobe or lobes. 
A still more complex canal system is 
hypothetically shown by text fig. 10. 
the subumbrella 
Transverse section of a 
Fic. 9.—Laotira cambria. 
complex specimen of the type of figs. 3, 3a, 5, and 5a 
of Pl. XIII. 
shown diagram- a, upper or exumbrella lobes; 0, oral arms with 
interior canal; g, interior canal corresponding to the 
upper central stomach in Brooksella and the simple 
form of Laotira. 
Tn 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. 
