146 A HISTORY OF RECENT CRUSTACEA 
CHAPTER XI 
SUB-ORDER II.—MACRURA 
THE carapace in general is shorter than the pleon and has 
the ‘front’ produced into a more or less decided rostrum. 
The stalked eyes are not enclosed in orbits, but usually 
rest in a hollow on the upper surface of the basal joint of 
the first antennz. Both pairs of antennz are generally 
elongate, the first not planted in fossettes, the second 
usually carrying a scale or acicle attached to the second 
joint. The third maxillipeds are elongated and pediform. 
The five pairs of pereeopods or limbs of the trunk vary 
greatly, as any of them may be chelate and any of them 
simple. ‘The sternal plastron or breastplate is linear in 
general. The vulvz of the female open in the basal joints 
of the third pair of legs, and the vasa deferentia of the 
male pass through those of the fifth pair. The pleon is 
seldom completely reflexed against the breastplate. Of 
the six pairs of pleopods the first varies from the succeed- 
ing, and all may be absent; but except in the Lithodidee 
that belonging to the sixth segment is always present, 
this pair with the telson forming the Rhijidura or tail-fan. 
Otoliths of some kind are very commonly present in the 
basal joint of the first antennze. 
In the above definition the Pterygurous division of 
Milne-Edwards’ Anomura is included. After explaining 
the grounds upon which Milne-Edwards had introduced 
his tripartite arrangement, de Haan makes the following 
comment upon it:—‘The division of the Decapoda into 
Brachyura and Macroura is for various reasons to be pre- 
