107 
Page 44. Diastylis Rathkei, var. 
(PI. LXX—LXX1I.) 
Remarks .— On page 45 I have mentioned that some forms of Diastylis 
Rathkei differ conspicuously from the type described by Kroyer, in their more 
spiny carapace, and apparently form a transition to the British species D. Bradyi 
Norman. These forms I propose to combine as a distinct variety, of which 
figures, both habitus and detail, are given in the last 3 plates. It will he seen, 
on comparing these figures with those given on PL XXXIII and XXXIV, which 
are from a typical specimen, that this variety exhibits several differences, not 
only in the form and armature of the carapace, but also in the structure of the 
several appendages. In my opinion, however, these differences are not great 
enough to warrant a specific distinction, and I therefore do not find it neces¬ 
sary to give any exhaustive diagnosis of this form. Meanwhile it may be of 
interest to call attention to some of the more conspicuous differences from the 
typical form. Whereas in the latter (see PI. XXXIII) only 3 small spinules 
are found on each side below the frontal lobe, there is in the present variety a 
considerable number of such spinules, giving the anterior part of the carapace a 
rather scabrous appearance (see PI. LXX). These spinules are even partly 
continued beyond the middle of the carapace along the most prominent part of 
the branchial regions. The spinules of the frontal lobe have a somewhat vari¬ 
able arrangement, being disposed in some specimens (see the 2 habitus-figures) 
in 2 or 3 transverse rows, whereas in other specimens (see the 2 figures of the 
carapace) they form 2 longitudinal rows, as in the tyjrical form. As to the 
shape of the carapace, a rather conspicuous difference is observed in the devel¬ 
opment of the subrostral corners, which in the typical form are distinctly pro¬ 
minent, whereas in the present variety they are almost obsolete, causing the 
anterior part of the carapace, when viewed laterally, to appear more conically 
tapered. The mucroniform processes of the last pedigerous segment in this 
variety always point straight behind, whereas in the typical form they are 
slightly divergent. In the structure of the appendages the following differences 
may be noted. On the superior antennm I have failed to detect any trace of 
the strong denticle found in the typical form at the end of the 1st peduncular 
joint. The 1st pair of legs appear somewhat more slender, with the outer joints 
more elongated, and this is also the case with the 2nd pair, the last joint of 
which in particular is conspicuously longer than in the typical form. The telson 
considerably exceeds in length the stem of the uropoda, and its lateral spinules 
are more slender and fewer in number than in the typical form. The outer 
