THE GENDERS OF GENERA 19 
The species Pseudocorystes armatus, Milne-Edwards, 
was found at Valparaiso, and Milne-Edwards supposes that 
it may be the same as the ‘ Grass Crab,’ figured by Browne 
in his ‘ History of Jamaica,’ pl. 48, fig. 2. 
Atelecyclus, Leach, 1813, is a member of the family in 
which the third maxillipeds, contrary to the family custom, 
do make a complete closure of the mouth-cavity. The 
type species, Atelecyclus septemdentatus (Montagu), was 
first observed on the south coast of Devon. Its carapace 
is nearly circular. Leach says that to the fishermen it is 
well known by the name of old man’s face crab. ‘The 
antero-lateral margin on each side is furnished with nine 
teeth, and probably for this reason Leach thought himself 
justified in changing the name to heterddon, in which he 
has been followed by Bell. Montagu perhaps did not 
think that the point at each extremity of the series ought 
to be counted in, and at any rate no one can be injured by 
the retention of the name which it was his privilege as 
the discoverer of the species to choose. 
Thia, Leach, 1815, is represented both in the Mediter- 
ranean and in British waters, probably by one and the 
same species, called Thia polita by Leach in 1815, in allu- 
sion to the polished surface of the carapace, but as there is 
no substantial reason for thinking it distinct from the 
species described and figured by Herbst as Cancer residuus 
in 1799, its name ought to be Thia residuus (Herbst), 
although some may prefer to call it Thia residua, not re- 
flecting that the animals are both male and female, and 
ignoring the old rule of Latin grammar that the mascu- 
line gender is to be preferred to the feminine. In this 
species, which hke Corystes is a sand-burrower, the pleon 
is very narrow in both sexes, and, though in the male it is 
only five-jointed, the transverse grooves of the composite 
joint are so strongly marked, that all the seven joints 
might at first glance be thought to be distinct, as they are 
in the female. 
To conclude the discussion of the names used in this 
family, it may be mentioned, first, that although de Haan 
rightly claims priority for Dicéra which he established 
