PLATE IT. 



Brooksella alternata (p. 23). 



Fig. 1. An exumbrella showing a more complicated system of lobes than those shown in figs. 8 or 



9 of PI. I. 

 Fig. la. View of the flattened surface of the subumbrella of fig. 1. 

 Fig. 2. An exumbrella in which the lobes are more distinct than in fig. 1. Numerous interum- 



brella lobes are shown projecting from beneath the exumbrella lobes. 

 Fig. 3. An exumbrella in which it appears as though a narrow-lobed exumbrella, like that of fig. 7, 



PI. I, had been superimposed upon a wide-lobed exumbrella. like that of fig. 1, PI. I. 

 Figs. 4, 4a, 4b. An irregularly lobed exumbrella which has the appearance of two narrow-lobed 



exumbrellas placed one upon the other, very much as one starfish would close down 



upon another. The side view of this specimen (fig. 4b) and the subumbrella (fig. 4a) 



show that the irregular exumbrella lobes join the subumbrella lobes, and that there is 



but one individual. 

 Fig. 5. Exumbrella having very narrow, rounded lobes, the surface of which is slightly roughened 



by semi-inosculating, irregular, raised and depressed lines. 

 Fig. 5a. Side view of fig. 5. 



Fig. 6. Narrow-lobed exumbrella showing the radial canals. 

 Fig. 6a. Side view of fig. (i. 

 Fig. 7. An exumbrella in which t lie surface of the lobes is roughened in the same manner as shown 



in tig. 5. 

 Fig. 8. Side view of an individual preserving 4 oral arms. 



Fig. 8a. Dorsal view of fig. 8. The canals of the oral arms are shown at x, x, .v. 

 Fig. 8b. Transverse section of fig. 8. showing the section of the canals and the oral arms at x, x, a 



radial canal of the exumbrella lobe at n. a trace of the central stomach (?) at //. and the 



lower portion of the pillar canals at c. The points at d, il may indicate the direction of 



the primitive oral aperture. 



108 



