1908] Decapod Urustaceans. 35 
east. 'The ova were globular, and the largest were 3 mm. in 
diameter. 
Maturity: From the above measurements it will be seen 
that 110 mm. was the length of the smallest berried speeimens as 
well as of those which had evidently cast their spawn. We have, 
however, one berried specimen from Jan Mayen 95 mm. long. Of 
the females over 110 mm. long, approximately half were berried 
and half had cast their spawn. 
Male and Female: Males as well as unberried females 
(excepting when these have just cast their spawn) have each of 
the posterior thoracic and of the abdominal segments armed on the 
lower side with å stout spine (fig. 2, Pl. X); whereas ovigerous 
(berried) females have in place of these spines merely å nodiform 
prominence (fig. 1); in addition to which, when the ova are removed, 
a deep hollow is seen to exist on the lower side of the abdominal 
segments. Moreover not only are there no spines on the abdominal 
segments of ovigerous females, but the pectiniform prominence on the 
lower side between the pereiopods is also to å great extent wanting. 
The females which had evidently just cast their spawn resembled 
the berried females in being without the spiniform prominences. 
The spines are proportionally larger in younger specimens than 
they are in older ones; and inasmuch as the berried females, in 
which spines are wanting, are all large specimens, one might be led 
to suppose that the want of spines is merely an age-characteristic, 
and that the spines are reduced in size with every moult. They 
are, however, always present, when the females are not ovigerous 
or have evidently just been berried. Indeed in the case of some 
specimens that were unbervried, but bigger than many of the ovigerous 
females, quite large spines were found developed; whereas spines 
were wanting in the whole of the ovigerous individuals, large and 
small. The presence of spines below the abdominal segments seems 
to depend upon whether the females are or have recently been 
ovigerous, though whether or not the spines are subsequently devel- 
oped, after the spawn has been cast, is as yet unknown. 
1st pair of Antennae show sexual differences. Like most 
of the Caridea the males of Selerocrangon ferox have larger and 
more stoutly developed antennae (ist pair) than the females. 
32 
