THE MYSWACEA 



181 



somites were distinct beneath the carapace in Pygocephalus, but in 

 the genus Crangopsis 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 

 slnthrapalaemon, may be found to possess Mysidacean 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 which link 

 together the individual orders. For example, 

 the retroverted palp of the maxillula in Gnatfw- 

 phausia is repeated in the Cumacea and Tanaidacea, Fio no 



and the branchial epipodite of the first thoracic p yg ocephaius 

 limb in these two orders mav be derived from m , the coai-measurea. 



., , . -i * i i Female specimen, from 



the simpler appendage found in the Mysidacea. i>eiow, showing the imt 

 The families mentioned below are those 



(Aflw 



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

 the Petalophthalmidae, established by Holt and Tattersall (following 

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

 have been regarded by Norman as distinct families. 



ORDER Mysidacea, Boas (1883). 



Family LOPHOGASTRIDAE. Lophogaster, M. Sars ; Gnathophaiisia, 

 Willemoes - Suhm (Fig. 100). Family EUCOPIIDAE. E-ucopia, Dana. 

 Family PETALOPHTHALMIDAE. Petalophthalmus, Willemoes-Sulmi ; Han- 

 senomysis, Stebbing. Family MYSIDAE. Sub-Family ARCHAEOMTSINAE. 

 Archaeomysis, Czerniavsky. Sub-Family LEPTOMYSINAE. Leptomysis, 

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

 Euchaetomera, G. O. Sars ; Amblyops, G. O. Sars ; Pseudomma, G. O. Sars. 

 Sub-Family ARACHNOMYSINAE. Arachnomysi^ Chun. Sub-Family 

 MYSIDETIXAE. Mysidetes, Holt and Tattersall. Sub-Family MYSINAE. 

 My sis, Latreille (Fig. 99) ; Macromysis, White (=Praunus, Leach). Sub- 

 Family STILOMYSINAE. Stilomysis, Norman. Sub-Family HETEROMYSINAE. 

 Heteromysis, S. I. Smith. Sub-Family MYSIDELLIXAE. Mysidella, G. O. 



