47 
Fam. 1. Spiriferid(B. 
The oral arms very largely developed, and supported the whole of 
their length by a thin, shelly, spirally twisted plate. Only known 
in the fossil state. 
1. Spirifer (fig. 29). 
Fig. 29 . — Spirifer ?. 
Fam. 2. Rhynchonellidee. 
The oral arms are elongate, fleshy, supported at the base by two 
short, hard, diverging shell-laminae arising from the hinge-margin 
of the ventral valve. 
1. Rhynchonella. 
1. R. psittacea, t. 381. f. 2 (fig. 30). 
Fig. 30 . — Rhynchonella psittacea. 
Order IV. Sarcobrachia. 
The oral arms fleshy to the base, and without any shelly support. 
The lower valve without any processes on the hinge-margin or disk, 
or except sometimes a slight medial longitudinal elongation. 
Fam. 1. Productidce. 
Shell generally spinose, attached by the surface of the ventral 
valve. Only found fossil. 
1. Productus. 
