282 ZOOLOGY 
This is not a large group, and its relation to the other 
Thoracostraca is the subject of much difference of opinion. 
The best-known genera are Diastylis (= Cuma) and Leucon. 
Among the points of interest presented by these animals are 
the following :—the second antennae, rudimentary in the 
female, are in the male as long as the body, a sexual dis- 
tinction which exists also in Nebalia. The mandible is with- 
out a palp, as in the Phyllopoda. There are only one pair of 
gills, which are of large size, and are borne by the second pair 
of maxillipedes. The two eyes lie close together, or have fused 
into a single mass, which, contrary to the usual rule in the 
Thoracostraca, is sessile. The brood-pouch, in which the eggs 
undergo their developement, is formed from processes, probably 
epipodites, of the fourth, fifth, and sixth thoracic legs, an 
arrangement which is also met with in the Schizopoda and 
the Arthrostraca. 
Little is known about the habits of these animals; they 
live together, usually on a sandy bottom, at considerable depths, 
they rest during the day and come to the surface and move 
about at night. 
Sub-order 2. STOMATOPODA. 
CHARACTERISTICS.— The carapace is short, and leaves a variable 
number of thoracic segments free. Portions of the head bear- 
ing the eyes and antennae are also free and moveable. There 
are five pairs of maxillipedes, and three pairs of biramous 
thoracic feet. The abdomen is large, and the abdominal 
appendages carry the gills. 
The Stomatopoda are animals of considerable size, the 
larger species of Squilla attaining a length of 7 or 8 inches or 
more. The carapace is short, and does not cover the three 
thoracic segments which bear legs; the five segments in front 
of these, which carry the five pairs of maxillipedes, are 
much shortened. The portion of the head bearing the eyes, 
and that carrying the antennae, are free and moveable, and the 
ventral portions of the segments covered by the carapace are 
also capable of a certain amount of movement upon one another. 
The six abdominal segments are large, and end in a broad telson. 
The first antenna consists of a basal shaft bearing three long 
