362 A HISTORY OF RECENT CRUSTACEA 
the Dinamene forms have the pleon not rugose and the 
uropods fixed some way up the terminal segment, and the 
branches not in any marked manner extending beyond it, 
nor separated from one another. The forms rubra and 
viridis are also without dorsal tubercles. No one appears 
to have ever found the Nesa form or Dynamene Montaqui 
carrying eggs, and, as they are not at all uncommon, they 
may, therefore, be presumed to be of the male sex. The 
differences between the female Dynamene and Nesa in the 
hinder half of the animal are superficially very great, but 
they are bridged over to a certain extent by the inter- 
mediate form of Dynamene Montagui. All the three forms 
agree In having both branches of the fourth and fifth pleo- 
pods furnished with transverse folds or pleats so as to be 
fully branchial. Dynamene in 1814 had as yet no species. 
Cymodoce, Leach, 1814. It is not easy to understand 
why authors have combined not only to adopt a different 
form of this name, but to base the alteration on Leach’s 
original authority. In this genus the pleon is dorsally 
tuberculate, with two apical notches, and the outer branch 
of the uropods so placed that it cannot completely close 
under the inner, both branches remaining always salient. 
The British species are Cymodoce truncata, Leach, and 
Cymodoce emarginata, Leach, the latter of which has not 
recently been found. Cymodoce Lamarckiu, Leach, from 
Sicily, is briefly described, and not in agreement with the 
generic definition. M. Eugéne Hesse has persuaded him- 
self, not only that Dynamene is the female of Nesa, which 
is possible, but that Spheroma is the female of Cymodoce, 
which certainly cannot be accepted on such arguments as 
he produces. As between British species assigned to the 
two genera, there is no resemblance of colouring worth 
speaking of, and no community of residence, except that 
Cymodoce is eccasionally and very rarely found on some of 
the shores that also yield Spheeroma. In Spheroma quadri- 
dentatum, Say, Mr. Harger has ascertained that neither 
sex 1s a Cymodoce. The curious fact remains that no 
ovigerous Cymodoce has yet been recorded. It is, perhaps, 
still more singular that the sexual characters in this group 
