FAMILY SPH#ROMIDA. 91 
prolonged examination that I could separate females, and 
especially half-grown specimens of the three species; the 
males will be far from easy to describe and figure well, but 
the specific characters in immature forms and females will be 
very difficult to describe and figure, so that even a careful 
student may be able to determine specimens when he has 
only a small material at his disposal. I should advise 
carcinologists not to establish species on females or immature 
specimens belonging to Cymodoce, Cilicwa, Cilicxopsis, 
Dynamene, Dynamenella, or Paracerceis if males be 
not at hand from the same locality. 
In some genera, as Cerceis (M.-Hdw.) and Dynamenella 
(n. gen.), the shape of the abdominal notch differs generally 
very considerably in adult males, immature males, and 
females. In Parasphzroma (Stebb.) there is a marked 
sexual difference in thickness and equipment with hairs and 
spines of some of the joints of second and third thoracic legs 
(a more detailed description is found in Chapter VII). In 
Monolistra (Gerst.), Vireia (Dollf.),and probably the other 
genera of the section Monolistrini the second thoracic legs 
are simple in the females, while in the males they terminate 
in a prehensile hand. In the section Ancinini (Ancinus) 
(M.-Edw.), Ancinella (n. gen.), Tecticeps (Richardson), 
the second legs are simple in the female, and terminate in a 
prehensile hand in the male, but in one of these genera, 
Tecticeps, we find besides a remarkable sexual difference 
in length and shape of sixth joint in seventh thoracic legs, and 
differences in the end of abdomen, length of exp. of urp., etc. 
V.—REMARKS ON STRUCTURAL FEATURES AND CHARACTERS. 
The head.—While in Cirolana and many other genera 
of Cymothoidee (sens. lat.) a frontal plate is very distinct and 
well marked off from clypeus, we find in Spheromidee only 
one plate, which has been named “epistome.”’ This epistome 
is always broad behind, its posterior margin at least con- 
spicuously and frequently so strongly concave that a deep 
rounded incision is formed; in such cases the posterior part 
