142 CRUSTACEA——-HOPLOCARIDA CHAP. 
costraca by a combination of characters, and Calman proposes 
the term HopiocaripDA for a division equivalent to the Peracarida, 
Eucarida, ete. 
The abdomen is very broad and well developed, ending in a 
widely expanded telson. There is a carapace which covers the 
four anterior thoracic segments, leaving the four posterior seg- 
ments free. The portion of the head carrying the stalked eyes 
constitutes an apparently separate segment articulated to the 
head. The antennae, mandibles, and maxillae are normal; there 
then follow five pairs of uniramous thoracic limbs turned forwards 
as maxillipedes and ending in claws; the second pair of these is 
modified into a huge raptorial arm, exactly resembling that of a 
Praying Mantis (ef. vol. v, p. 242), by means of which the 
Squilla seizes its prey. The last three thoracic limbs are 
small and biramous. The pleopods are powerful, flattened, 
biramous swimming organs with small hooks or “ retinaculae ” 
upon their endopodites, which link together each member of a 
pair in the middle, and with large branching gills upon the 
exopodites. 
The internal anatomy exhibits several primitive features. The 
nervous system is not at all concentrated, there being a separate 
ganglion for each segment ; and the heart stretches right through 
thorax and abdomen, with a pair of ostia in each segment. 
There are also ten hepatic diverticula given off segmentally from 
the intestine. 
The female has the curious habit of carrying the developing 
egos in a chamber improvised by the apposition of the maxilli- 
pedes, so that it looks rather as if she were in the act of 
devouring her own brood. 
The metamorphosis of the larvae, despite the work of Claus? 
and Brooks,” is not very accurately known, especially uncertain 
being the identification of the different larvae with their adult 
forms. The chief interest consists in the fact that certain of 
the anterior thoracic limbs develop in their normal order and 
degenerate, to be reformed later, just as in the Phyllosoma larva 
of the Loricata (see pp. 165, 166). 
In one series of larvae, probably not of Sqwilla itself, but of 
related genera, the young hatch out as “ Erichthoidina” (Fig. 99), 
l Abhandl. kénigt. Gleselisch. Gottingen, xvi., 1871. 
2 Mem. Nat.\Acad. Sci. v., 1891. 
