90 H. J. HANSEN. 
In several genera, viz. Spheroma (Bosc), Cymodocella 
(Pfeff.), Scutuloidea (Chilt.), Amphoroidea (M.-Edw.), 
Cassidinopsis (n. gen.), Cassidinidea (n. gen.), Lepto- 
spheroma (Hilg.), Limnoria (Leach),and Plakarthrium 
(Chilt.), there are at most rather slight sexual differences in 
shape of thorax, abdomen, thoracic legs or uropoda; but in 
some of them the males are larger than the females. In other 
genera, as Isocladus (Miers), Zuzara (Leach), Cymodoce 
(Leach), Cilicza (Leach), Ciliacewopsis (n.gen.), Bregmo- 
cerella (Hasw.) Dynamene (Leach), Paracerceis (n.gen.), 
adult specimens of the two sexes differ exceedingly from 
each other in various respects; the males are distinguished by 
processes on sixth or seventh thoracic segments or on the first 
portion of abdomen, shape of uropoda, frequently shape of 
the end of abdomen, etc., in Bregmocerella even processes 
on the head. Leach established some genera on adult males, 
referring the majority of females and young specimens to 
Spheroma or Dynamene, the latter of which was estab- 
lished exclusively on such specimens. Similar confusion is 
still found in papers published in the last six years. In 1873 
Hesse stated the species of Spheroma are female of Cymo- 
doce, Dynamene females of Nesa. As to the European 
forms of Dynamene it is quite correct (exotic forms referred 
to Dynamene cannot remain in this genus), but regarding 
Spheeroma the case is more complicated ; among the Euro- 
pean forms referred to the latter genus, those without terminal 
notch are well-founded species—with males and females— 
of Spheroma itself, while those possessing an abdominal 
notch are females or young males of Cymodoce or other 
genera. Miers has correctly referred females and males of 
some exotic species of Cymodoce, but he did not undertake 
a special study of the family. It is scarcely necessary to give 
here a detailed account of the sexual differences alluded to 
in these genera; the notes in the systematic chapters may be 
sufficient. But one thing must beadded. At Sicily I collected 
a rich material of three species of Cymodoce; while the 
adult males were not difficult to separate, it was only after a 
