Genera of the Xoeth American Palaeozoic Bryozoa. 447 



stomach (Plate B, %. a\ an oblong cavity terminating below 

 in a blunt extremity. From the upper part of the stomach, near 

 the gizzard, by a true pyloric cavity (fig. 5, a), arises tbe intestine, 

 which continues nearly straight, alongside the oesophagus, and 

 terminates by a distinct anal orifice, close to the outer side of the 

 lophophore. Thus the alimentary canal consists of pharynx, 

 oesophagus, gizzard, stomach and intestine, with distinct oral, 

 cardiac, pyloric and anal orifice. 



The whole floats freely in the perigastric cavity, the boundaries 

 of which are the walls of the cell, and which contains the peri- 

 gastric fluid and the muscles of the animal. 



In Paludioklla, the upper part of oesophagus is wide (the 

 pharynx) but soon contracts and continues as a long narrow tube, 

 which leads into an oval sac (Plate A, fig. 1, c\ corresponding to 

 the gizzard of the marine forms and to the cardiac cavity of the 

 stomach of the Hippocrepian forms. This sac is much more 

 distinctly expanded from the large cavity of the stomach (the 

 pyloric cavity) than in the other fresh-water forms. When 

 the animal is completely retracted it is bent backward upon 

 the pyloric cavity (Plate A, fig. 2, c). The intestine arises from the 

 upper portion of the pyloric cavity (Plate A,/). 



In the Hippocrepian forms, the oesophagus becoming narrower 

 and opening into the stomach with a distinct conical projection. 

 In the contraction of the animal within its cell, in these 

 forms, the alimentary canal occupies essentially the same 

 relative position as when the animal is protracted, the oesophagus 

 remaining straight; but in Paludicella and in the marine forms, 

 the alimentary canal is doubled upon itself and its form is some- 

 what modified (Plates A and B). The lophophore is brought 

 down to the upper part of the stomach ; the intestine is doubled 

 upon itself, and the oesophagus is forced down to the side of the 

 stomach, and again turning upward has somewhat the form of 

 the letter S. The stomach is composed of three different layers ; 

 the inner one of which has frequently longitudinal ridges 

 (fig. 20, d)^ though this feature is often absent. The layer is com. 

 posed of easily separable spherical cells, which contain a smaller 

 cell or nucleus, floating in a colorless liquid having yellowish- 

 brown contents (fig. 18, a, h). These are, in all probability, hepatic 

 follicles, secreting a fluid which colors the stomach and its con- 



