Two new Spiders from Demerara. 143 
frequent the coral-reefs and rocky pools of the Austro-Malayan 
and New Zealand seas. ‘To discover, if possible, whether their 
mode of life has affeeted their breathing-organs in any way 
comparable to what has occurred in Argyroneta, I examined 
specimens of Desis Martensii from Singapore and an example 
of Robsonia marina from New Zealand, with the immediate 
result of finding a conspicuous slit-like tracheal aperture in 
the posterior half of the abdominal region, but well in advance 
of the spinning-mammille. The shape of the aperture is 
slightly procurved ; its anterior lip is smooth and at the sides 
has a thickened horny rim, which defines more clearly the 
position of the trachea inside. In one specimen in which the 
aperture was more agape than in others there appeared to be 
a distinct membranous partition passing from the anterior to 
the posterior wall of the cavity, apparently indicating that, 
although the two stigmata are sunk within a fold of the 
integument, no actual union between them has taken place. 
Now these two genera, Dests and Robsonia, are usually 
referred to the family Agalenide ; but it appears to me that 
this anterior position of the tracheal stigma, taken in conjunc- 
tion with other well-established peculiarities of these spiders, 
justifies their elevation to the rank of a special family, which 
may be called Deside. 
Another interesting fact, moreover, has beenascertained from 
looking into the literature of this group. This is the identity 
between the spider named Dandridgia dysderoides by White 
and Robsonia marina by Hector. The latter was described by 
its author as an Argyroneta, but it subsequently received the 
name fobsonia from the Rev. O. P. Cambridge. The last- 
named author considered this genus to be different from 
Desis of Walckenaer. ‘The type of the latter genus I unfortu- 
nately do not know ; but it appears to me to be very doubtful 
whether the New Zealand marina can be looked upon as 
generically distinct from the Singapore species Martensit. 
They seem to be nothing but well-marked species of the same 
genus, as Mr. Powell supposed. If this be so, the synonym 
of the species will stand as follows :— 
Desis marinus (Hector). 
Dandridgia dysderoides, White, Proc. Zool. Soc. 1849, p. 5 (the specific 
name dysderoides being preoccupied by Walckenaer for the type 
species of Desis cannot be maintained for this one), 
Argyroneta marina, Hector, Tr. N. Z. Inst. x. p. 399 &e. (1877). 
Desis Robsoni, Powell, Tr. N. Z. Inst. xi, p. 268 (1879). 
Robsonia marina, Cambr. Proc. Zool. Soc. 1879, p. 686. 
If, however, this species is generically distinct from the 
type of Desis, it must be known by the names that White 
ascribed to it. 
