TftOPODS OK NORTH AMERICA. 



133 



sand, the .surfiicc of wliicli is iilmost doiihlcd. This increase in the 

 measure of the eye is not an eti'ect of the increase in size of the 

 figure, fori?, ddderlemi Ortinaiui has the ocelli almost as larg-e and as 

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

 abyssal life. In order to collect in the g-reatest number the feeble 

 phosphorent rays which lighten the depth of the seas, the ej^es of 

 ButhynoriiKM are greatly oidarged and resemble the eyes of ab^^ssal 

 (xalatheides (Munida), in which the deticiencA' of the lig-ht at the great 

 (h^pths has not yet produced blindness. 



In the two species of Batli.ytwiiius he has been able to prove that 

 the sympodite of the pleopods has alwaA-s three articles, that it is 

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

 accessor}" appendage exists at the apex of this peduncle. The pres- 

 ence of this accessory appendage is a primitive character which brings 



Fi(i. 115.— Bathyxomus giganteus (After Ei>wARr>s and Bouvikr). Lateral view. 



the Bdthynomus, and consequently the Cirolanida?, 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 Hrst 

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

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



25. Genus COLOPISTHUS Richardson. 



Head transversel}^ elongated. E3'es situated in the middle of the 

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

 surface. 



Both pairs of antenna? short; tirst pair of antenna^ with basal article 

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

 ing ]iart of antenna; second pair reach the posterior margin of the 

 tirst thoracic segment. 



First five abdominal segments consolidated into one short segment. 

 Terminal segment strongly 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 po^iition of the fir^tt joint. 



