48 
Fam. 2. Craniadoe. 
The upper valve conic ; the lower valve entire, flat. Attached to 
marine bodies by its outer surface. 
1. Crania. 
1. C. personata, t. 380. f. 1, 2, 3, t. 381. f. 5 (fig. 31). 
Fig. 31 . — Crania personata. (Dorsal surface.) 
Fam. 3. Discinidce. 
The upper valve conical, patelloid ; the lower orbicular, with a 
small slit in its disk, through which a short tendinous peduncle is 
emitted, by which it is attached. 
1. Discina. 
1. D. Cumingii, t. 381. f. 9 (fig. 32). 
Fig. 32 . — Discina Cumingii. (Lower surface.) 
p , peduncle. 
The valves free, nearly equal, elongate, and supported by a thick 
peduncle, which comes our "between the beaks of the two valves. 
Periostraca hard, olive. Shell sometimes very thin, almost flexible. 
