254? SUPPLEMENT 



trituration. The latter have those parts combined, so as to 

 form a sort of sucker or siphon. But as the buccal organs 

 have been already described with some detail both here and 

 in the text, we shall confine ourselves now to those of nutri- 

 tion, properly speaking. 



The intestinal canal of the Crustacea is generally short and 

 straight, and often in the course of its passage presents a re- 

 markable dilatation, which is the stomach ; but sometimes the 

 stomach is apparent only by a very slight enlargement of this 

 canal. The oesophagus is short. 



The stomach, as we have said, varies : that of the decapods, 

 both brachyurous and macrourous, placed above, and a little 

 in front of the mouth, occupies a very considerable space un- 

 der the anterior portion of the carapace. It is very capacious, 

 membranaceous, and its parietes are supported by complicated 

 cartilaginous arches, which keep them apart, even when the 

 stomach contains no food. Its figure is that of a trapezium, 

 the angles of which are rounded in the form of lobes, and of 

 which the two largest are anterior. In the middle of the 

 upper paries, we are told by M. Cuvier, that there is a trans- 

 verse cartilaginous ridge, which has within a first tooth, or 

 oblong osseous plate, fixed to its external face, directed 

 towards the pylorus, and terminating behind in a tubercle. 

 On their posterior extremity is articulated a second ridge, 

 directed backwards, bifurcated like a Y, and on each of the 

 lateral branches of this another is articulated, which returns 

 in front and externally, to arrive at the lateral extremity of the 

 first ridge. It is on these two lateral ridges that the largest 

 pyloric teeth are inserted : they are solid, oblong, and have a 

 flat crown furrowed crosswise, and its inequalities and furrows 

 vary according to the species. From the point of union of 

 the transverse and lateral ridge on each side proceeds another 

 lateral ridge, which goes lower than the first, and bears at its 

 extremity a lateral tooth smaller than the preceding, placed a 



