272 



CRUSTACEANS. 



Eupliausiidce, are hatched in the Nauplius stage. Most Schizopods are small, but 

 species belonging to the genera Lophogaster and Gnathophausia measuring as 

 much as 6 inches in length have been obtained. To the family Mysidce belongs 

 the genus My sis, or opossum-shrimps, among which is M. veheta from certain lakes 

 in Northern Europe. Into these lakes the species is presumed to have entered 

 while they were connected with the sea ; a supposition borne out by the fact that 

 it is nearly related to M. oculata, now living in the Arctic Ocean. 



THE MANTIS-SHRIMPS, Order STOMATOPODA. 



The mantis-shrimps (Squillidoe), which owe their name to the resemblance 

 that their seizing limbs bear to those of the insect mantis, are abundant in tropical 



seas, where they sometimes reach a large size. 

 Although bearing a general likeness to the long- 

 tailed Decapods, they may be recognised by 

 certain prominent characters. A glance at the 

 accompanying figure will show that the carapace 

 is so short as to leave the hinder segments of 

 the thorax uncovered, and, since the gills are 

 attached to the abdominal limbs, it forms no 

 branchial chamber. Only three pairs of limbs 

 are modified into jaws, these being the mandibles 

 and two pairs of maxillae. The remaining eight 

 pairs of thoracic limbs are foot-like, the large 

 prehensorial pair corresponding to the second 

 maxillipedes of a Decapod. Two kinds of 

 mantis-shrimp are occasionally met with in the 

 English Channel, namely, Squilla desmaresti 

 and S. mantis. The former is not uncommon 

 along the shallower parts of the shores of 

 Jersey, but as it lives in deep burrows among 

 the roots of sea-grass, in a zone never uncovered 

 by the tide, its appearance is infrequent. The 

 allied North American Lysiosquilla excavatrix 

 is found in the sand below low -water -mark, 

 where it is protected from the full force of the 

 ocean swell, and inhabits deep cylindrical 

 burrows which are nearly vertical and go down 

 MANTIS-SHRIMP (reduced). for several feet. 



Sessile-Eyed Series, EDRIOPTHALMATA. 



We now come to the second great series of the Malacostraca, in which the 

 compound eyes are generally sessile, and never mounted on movable stalks. As a 

 rule, the last seven segments of the thorax are not covered by the carapace, and 

 the last four are always free. The first order, Cumacea, is in many respects inter- 



