SESSILE-EYED SERIES 



3239 



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 cylin- 

 drical burrows which are nearly vertical and go 

 down for several feet. 



SESSILE-EYED SERIES EDRIOPTHA^MATA 



We now come to the second great series of 

 the Malacostraca, in which the compound eyes 

 are generally sessile, and never mounted on mov- 

 able 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 intermediate 

 between the typical members of the last and 

 present series, the thorax being larger and broader 

 than the abdomen, while the carapace covers all 

 but the last five segments. The front angles of 

 the carapace are produced to meet in a kind of 

 beak in front of the head, and the eyes are gener- 

 ally united in a single cluster of ocelli. None 

 of the thoracic limbs are prehensile or chelate. 

 The first five segments of the abdomen have no 

 appendages in the female, although such limbs 

 are present in the male. In the sixth segment 

 appendages are present in both sexes, and form a 

 fork-like termination to the body. Two of the 

 best-known genera of the group are Cuma and 



Diastylis. The order, however, is relatively a small one, containing only a little 

 over a hundred species. It has, nevertheless, a wide distribution, forms being met 

 with in shallow and deep water in all seas, although the Arctic Ocean produces in- 

 dividuals of the largest size and in the greatest abundance. 



MANTIS SHRIMP (reduced). 



Order ISOPODA 



Unlike the last, this second order of the series exhibits great diversity of struc- 

 ture. As a rule, the posterior seven segments of the thorax are free, and at least 

 the first three, and generally the first five segments of the abdomen are short and 

 sometimes fused together, while the sixth is the largest, and bears the telson and a 

 pair of appendages. The other abdominal appendages usually overlap, and are 

 modified to act as gills. The seven thoracic limbs are generally large, and per- 



