THE TELSON OF THE MACRUROUS CRUSTACEA. 95 
calcified continuously across its ventral surface, as the other segments 
are; but this appearance would arise from the small size of its real 
centrum, which, as in Scyllarus, would be quite anterior, and the © 
coalescence in the middle line of the proximal portions of the endo- 
podites of the segment. In the telson of the lobster, by looking at 
its dorsal surface obliquely, a system of undulations is observed, 
which corresponds, though in a much more disguised form, with the 
condition in Scyllarus, the two extreme lateral pieces with the accom- 
panying spines being easily seen, and the small elevated centrum at 
the anterior part. 
In conclusion, an attempt has been made to show (1), That in some 
Macrurous Crustacea, and therefore probably in all, the telson is a 
true body segment with lateral appendages, which are modified by 
cohesion and adhesion. (2) That the body of the segment terminates 
posteriorly in front of the anus, and that the cohesion of the endopo- 
dites superiorly causes the anus to be ventral. 
ie i \Central Element 
{ Endopodite 
Propod ite 
Telson, &e., of Scyllarus arctus. 
