THE MYSIDACEA i8i 



somites were distinct beneath the carapace in Pygocephahis, but in 

 the genus Crangopds of Salter, from the Lower Carboniferous, 

 Ortmann has shown that at least four somites are distinct. It 

 is probable that other fossil genera, such as the Carboniferous 

 JnthrajKilaemon, may be found to possess Mj'sidacean characters. 



Affinities and Classification. 



The removal of the Mysidacea from their old association with 

 the Euphausiidae in the group " Schizopoda " is 

 justified by the fact that the two groups do not 

 have in common any characters except those of 

 the primitive caridoid facies which they share 

 with the lower Decapoda and, in part, with the 

 Stomatopoda. On the other hand, the con- 

 nection of the Mysidacea, through the Cumacea 

 and Tanaidacea, with the Isopoda and Amphi- 

 poda is shown not only by the characters given 

 in the definition of the division Peracarida, but 

 also by many connecting characters Avhich link 

 together the individual orders. For example, 

 the retroverted palp of the maxillula in Gnatho- 

 phmisia is repeated in the Cumacea and Tanaidacea, ^ 



and the branchial epipodite of the first thoracic ry^J^^s' coopen, 

 Jmib in these two orders mav be derived from '^i;"'" t'le Coai-measures. 

 the simpler appendage found in the Mysidacea. beiow.'shXTn^the i,ni?r'i- 



The families mentioned below are those wood«^Kj.f '''' ^^'''' 

 accepted by G. 0. Sars, with the addition of 

 the Petalophthalmidae, established l)y Holt and Tattersall (following 

 Czerniavsky). The sub-families of the Mysidae as adopted here 

 have been regarded by Xorman as distinct families. 



Order Mysidacea, Boas (1883). 



Family Lophogastridae. Lophogaster, M. Sars; Gnathophansia, 

 Willemoes - Sulim (Fig. 100). Family Eucopiidae. Eiicopia, Dana. 

 Family Petalophthalmidae. Petalophthahnits, Willenioes-Suhm ; Han- 

 senomysig, Stebbing. Family Mysidae. Sub-Family Archaeomysinae. 

 Archaeomysis, Czerniavsky. Sub-Family Leptojiy.sixae. Leptomysis, 

 G. 0. Sars ; Erythrops, G. 0. Sars ; Dactylerythrops, Holt and Tattersall ; 

 Euchaetomera, G. 0. Sars ; AmUyops, G. 0. Sars ; Pseudomma, G. 0. Sars. 

 Sub-Family Arachnomysixae. Arachnomysis, Chun. Sub-Family 

 Mtsidetixae. Mysidetes, Holt and Tattersall. Sub-Family Mysinae. 

 Mxjsis, Latreille (Fig. 99) ; Macromysis, White { = Praunus, Leach). Sub- 

 Family Stilojiysixae. Stihmysis, is^ornian. Sub-Family Heteromysixae. 

 Heteromysis, S. I. Smith. Sub-Family Mysidellixae. Mysidella, G. 0. 



