THE MYSIDA 267 
maxillipeds have usually a natatory exopod, and an epipod 
projecting within the branchial cavity. The second pair are 
modified to serve the mouth. ‘The remaining appendages 
of the trunk are uniform, rather feeble, the terminal part 
generally subdivided into short setiferous articulations, 
the finger being small or wanting. There are no true 
branchize. The marsupium is composed of seven or more 
often of only two or three pairs of plates. The pleo- 
pods in the female are as a rule quite rudimentary, in the 
male either natatory or modified for sexual purposes. The 
inner branch of the uropods usually contains an audi- 
tory apparatus. The development is without any free 
metamorphosis. 
The eighteen genera included in this family by Sars 
in 1885 are Mysis, Latreille, 1803, Siriella, Dana, 1850, 
Promysis, Dana, 1850, Anchidlus, Kroyer, 1861, Hetero- 
mysis, S. I. Smith, 1874, Petalophthalmus, v. Willemoes 
Suhm, 1879, and the following twelve all instituted by 
Sars himself, Amblyopsis, Boreomysis, Hrythrops, Hemimysis, 
Leptomysis, Mysideis, Mysidopsis, Parerythrops, Pseudomma, 
under the common date of 1869, Mysidella, 1872, Macropsis, 
1876, and Euchetoméra, in 1883. The list (no doubt acci- 
dentally) omits a nineteenth genus, Pseudomysis, Sars, 1880, 
and a twentieth, Gastrosaccus, Norman, 1869, from which 
yet another has been severed in Haplostylus, Kossmann, 
1880. From Siriella Claus has separated Pseudosiriella, in 
1884. From Mysideis Norman in 1892 distinguishes Stilo- 
mysis, and in the same year recognises Macromysis, White, 
1847, Neomysis, Czerniavsky, 1882, and a new genus 
Schistomysis, as distinct from Mysis. Thus with Arctomy- 
sis, Hansen, 1887, added since Sars drew up his list, and 
with Arachnomysis, Chun, the number of genera, if all are 
accepted, amounts to twenty-eight. But further, Nor- 
man has called my attention to Czerniavsky’s Monographia 
Mysidarum, 1882-38, in which several new but not always 
well-founded genera appear. One of these preoccupies the 
name Arctomysis, so that Hansen’s genus must be re-named. 
Macromysis also must yield to the rather queer but much 
earlier generic name Praunus, Leach, 1818, of which the 
