446 



Report of the State Geologist. 



The tentacular crown may be divided into two portions : the 

 disc which surrounds the mouth and to which is given the name 

 lophophore, and the tentacles which are inserted on the margin 

 of the lophophore. 



In all the marine species and in one fresh-water species, 

 Paludicella Ehrenbergi, the lophophore is continuous around 

 the mouth ; the tentacles being arranged in a complete circle. In 

 the other fresh-water forms the arrangement is bilateral. The 

 lophophore is extended in two triangular arms ; the tentacles, ar- 

 ranged continuously on the margin of the disc and the arms are 

 disposed in a horseshoe form. From the mouth descends the 

 oesophagus ; at first a little expanded, then contracting and con- 

 tinuing nearly straight to its terminus. The upper, expanded 

 portion may be called the pharynx. The walls are thickly 

 studded with minute oval spots. In the marine species the oeso- 

 phagus leads into an oval sac, which performs the office of a 

 gizzard (Plate B, ^g. a, 3). The walls of this cavity are thicker 

 than those of any other portion of the alimentary canal. In the 

 walls are two dark bodies, opposite to each other (fig. 16), with radi- 



16a. 



16&. 



Fig. 16a. Bowerhankia clensa, showing the dark bodies of the oesophagus separated ; the cardiac 

 teeth showing between them. 

 Fig. 16b. Showing the dark bodies in apposition. 

 Fig. 1?. An enlargement of the cardiac teeth (after Farre). 



ating lines, and in the walls between these bodies are the cardiac 

 teeth (fig. 17), which present a somewhat regular tesselated appear- 

 ance. This again opens downward into the true digestive 



