ISOPODS OF NORTH AMERICA. 133 



sand, the .surface of which is almost doubled. This increase in the 

 measure of the eye is not an effect of the increase in size of the 

 figure, for B. doderleini. Ortmann has the ocelli almost as large and ;is 

 numerous as B. giganteus; it is entirely the result of adaptation to 

 abyssal life. In order to collect in the greatest number the feeble 

 phosphorent rays which lighten the depth of the seas, the eyes of 

 Bathynomus are greatly enlarged and resemble the eyes of abyssal 

 Galatheides (Munida), in which the deficiency of the light at the great 

 depths has not yet produced blindness. 



In the two species of Bathynomus he has been able to prove that 

 the sympodite of the pleopods has always three articles, that it is 

 the same for the peduncle of the antennuke, and that a rudiment of an 

 accessory appendage exists at the apex of this peduncle. The pres- 

 ence of this accessory appendage is a primitive character which brings 



FIG. 115. BATHYNOMUS GIGANTEUS (AFTER EDWARDS AND BOUVIER). LATERAL VIEW. 



the Bathynomus* and consequently the Cirolanidae, closer to the group 

 of Anisopods. 



Hansen points out that the peduncle of the second pair of antennse 

 is really composed of six articles in this form and others, but the first 

 article is so small it has heretofore been overlooked/' Apparently the 

 peduncle of the second antenna 1 is composed of five articles. 



25. Genus COLOPISTHUS Richardson. 



Head transversely elongated. Eyes situated in the middle of the 

 lateral margins at the extreme edge and elevated knob-like above the 

 surface. 



Both pairs of antennse short; first pair of antennae with basal article 

 of peduncle not extended straight in front at right angles to remain- 

 ing part of antenna; second pair reach the posterior margin of the 

 first thoracic segment. 



First five abdominal segments consolidated into one short segment. 

 Terminal segment strong!} 7 keeled in the median longitudinal line. 



"Edwards and Bouvier describe the peduncle as six-jointed, but, according to 

 Hansen, they were in error in regard to the position of the first joint. 



