404 CONTRIBUTIONS TO MARINE BIONOMICS. 
male.” On account of the presence of these spots Risso named the 
species Portunus biguttatus, portune & deux taches, portune bimaculé 
(p. 25). 
Costa, on the other hand (Addizioni, 1853, p. 11), describes the colour 
as “livid olive-brown tending towards purple; that of the feet and of 
the inferior face more pallid. In fresh specimens one may sometimes 
observe two rose-coloured spots in the middle of the carapace, which 
vanish after death.” 
Of my own specimens the larger one was of a uniform dull greenish 
yellow colour, the smaller one having the carapace and basal joints of 
the legs absolutely white, and the two terminal joints of the four 
posterior pairs of thoracic legs coloured pale brown and amethyst-violet. 
No reddish spots were visible in the living specimens. It is possible 
that these spots are only to be observed in the breeding season, and 
that they are due to the colour of the reproductive glands showing 
through the carapace. Such a phenomenon is at any rate described by 
Risso for Lathynectes longipes. He states (1816, pp. 30, 31): “La 
femelle, dans le temps des amours, est ornée de deux grandes taches 
d'un rouge foncé sur la partie antérieure du tét.” The eggs of the 
latter species are described as “d’un rouge aurore,’ which would 
sufficiently account for the red colour of the ovarian regions before 
deposition of the ova; those of P. nasutus are described as “d'un 
jaune doré.” Risso states that the eggs of P. nasutus are laid in May 
and August. 
5. SAND-BURROWING HabBiTs. 
The habits of Portumnus nasutus have hitherto been very imperfectly 
described. Risso (1816, pp. 25-31) states simply that at Nice the crab 
inhabits “la région des polypiers corticifcres” (p. 25), or ‘la région des 
coraux” (p. 31). Latreille’s specimen (1825, p. 151) was obtained by 
D’Orbigny on the coast of La Vendée, which probably implies a sandy 
habitat, especially as Latreille’s specimens of “ Platyonichus variegatus ” 
(Portumnus latipes) were obtained by the same naturalist on the same 
coast (Nouv. Dict. d’ Hist. Nat., 1818), and the latter species is known 
to have sand-burrowing habits. 
My own observations are, however, unequivocal. The specimens 
were found burrowing in coarse shelly gravel, and when the crabs were 
introduced into an aquarium containing a deep layer of the same gravel 
they were observed to burrow into it at once with extreme agility until 
their bodies were completely covered to a depth of an inch or more, 
The act of burrowing is effected by means of the hinder thoracic legs, 
as is usual among Portunids. The crabs can also burrow in fine siliceous 
sand. 
When imbedded, P. nasutus seems always to adopt a nearly horizontal 
