Vig. 1. 
Fig. 2. 
Fig. 3. 
Fig. 4. 
Fig. 5. 
Figs. 6 
Fig. 7 
Fig. 8 
Fig. 9. 
Fig. 10 
Fig. 11 
Fig. 12 
Fig. 13 
Fig. 14. 
PLATE XI. 
Portion of the lower side of the disk, showing a part of the white plate ss, with the ramifications 
of the liver UJ, and the course of the tubules ft, which have passed through the white plate, 
with portions of the corrugations of the lower side of the circular chambers c. 
Diagrammatic sketch showing the relative position of the disk, of the edge of the white plate, and 
of the mantle. 
Central chamber a, with the adjoining chambers from which lead the first rows of tubules t. 
Cluster of tubules on the dorsal side of the white plate. 
Corrugations of three of the inner chambers of the lower side of the disk, showing the short 
tubules and their mode of attachment, about under the white plate. 
, 6. Greatly enlarged view of a few joints of one of the tubules. 
Part of the outer portion of the disk, showing the arrangement of the stigmata 0, on the upper 
surface. 
Slightly oblique view of the cross-section of the outer part of the disk showing the position of the 
stigmata oo, of the successive chambers aa, and of the primary and secondary corrugations on 
the lower side, ¢ and c’, of the circular chambers, and the mode of attachment of the 
tubules ff. 
Different profile view of a portion of the disk. Lettering as before. 
Shows the general arrangement of the simple corrugations, v, of the lower side of the circular 
chambers, in a young specimen. 
Portion of the lower side of the disk showing the folds of the lower side of the chambers, ¢ ¢’, as 
older far as the last outer cireular wall, ppp, of the disk. 
Portion of the disk of a young Porpita, ,/’ in diameter, with four circular chambers ; 0’—-o*, stig- 
mata, ff’, fold in the chambers corresponding to the original eight chambers, and forming in 
older specimens the irregularly radiating lines of the upper side of the disk. 
Slightly oblique end view of a part of the corrugations, c c’, of the last chamber of the edge of 
the disk. 
An end view of a few corrugations of a similar part of the disk, 
