238 
SUPPLEMENT 
neath this testa of very distinct segments, and these segments 
themselves are composed of several pieces. The under part 
of the body in the brachyurous decapods presents a surface 
more or less extensive, which may be compared to the breast- 
plate of the tortoises. Its middle is hollowed by a gutter or 
furrow, more or less broad, more or less prolonged in front, 
but, in general, of a greater extent in the females than in the 
males. This lower surface of the breast-plate is composed of 
two orders of pieces : the first, which are medial, and much 
larger than the others, are called sternal pieces ; the others, 
being lateral, are termed later o- sternal pieces. Between these 
pieces and the lateral and inferior edges of the carapace, are 
situated the feet. 
Among the entomostraca, some, as apus and branchipes, 
have the body annulated underneath, as well as above, and 
have no traces of latero-sternal pieces, while others have no 
indication of divisions whatsoever. 
The name of tail or abdomen is reserved for the terminal 
part of the body, which contains only the posterior part of the 
intestine. The anus is at its inferior face, to which also the 
branchial, feet are sometimes attached. In some Crustacea, it 
contains the organs of generation ; and in many it is furnished 
at its extremity with natatory appendages. In the decapod 
Crustacea, this tail is always folded under the body, and closes 
the furrow or longitudinal gutter of the sternum. It forms 
uith this furrow a sort of box, in w hich the eggs are received 
and lodged at the period of laying. The tail of the males is 
placed entirely in this furrow. 
The macrourous Crustacea have received this appellation in 
consequence of the extent of the tail 5 it is sometimes soft, 
and without distinct rings, as in pagurus, sometimes very 
solid and very muscular. A most remarkable circumstance is, 
that the paguri betake themselves to the cavities of univalve 
shells, and that the spiral form of these cavities takes away 
