142 CRUSTACEA — HOPLOCARIDA chap. 



costraca by a combination of characters, and Caiman proposes 

 the term Hoplocarida for a division equivalent to the Peracarida, 

 Eucarida, etc. 



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 (cf. 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 

 eggs 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 Glaus ^ 

 and Brooks,^ is not very accurately known, especially uncertain 

 being the identification of the dilTerent 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 SquUla itself, but of 

 related genera, the young hatch out as " Erich thoidina " (Fig. 99), 



' Abhandl. Icbnigl. GesellscTi. Giittingen, xvi. , 1871. 

 ^ Mem. Nat. Acad. Sci. v., 1891. 



