REV. A. MERLE NORMAN, M.A., ON THE CRUSTACEA. 21%. 
The peduncle of the caudal appendages (Pl. XIV., fig. 66) is 
slender and not furnished with either spines or cilia. The rami 
are equal in length to the peduncle, the inner three jointed, the 
outer two jointed. The first joint of the inner ramus is longer by 
one-third than the corresponding joint of the outer ramus, but 
on the other hand, the second joint of the inner ramus is shorter 
by one-third than the second joint of the outer, and thus the two 
joints of both rami taken together are nearly equal. The first 
joint of the inner ramus has two or three minute spines on the 
exterior margin, and two slender spines at the distal extremity 
of the inner margin; the second joint has about four slender spines 
on the inner margin, but none on the outer; the third joint is 
tipped with a minute cilium. The first joint of the outer ramus 
has two slender spines, and both margins of the second joint 
haye three or four slender spines. 
Taken 100 miles east by north from Tynemouth, in 20-25 
fathoms, sand. 
We have yet much to learn respecting the Diastylide. We 
know little of what must be considered generic characters among 
these Sessile-eyed Stomopods, still less what are to be regarded as 
sexual, and what as specific distinctions. The generic characters 
ascribed by Mr. Spence Bate to Vaunthompsonia or Cyrianassa 
will require much revision, so as to embrace the species described 
in the present paper. In the allied family of the Myside con- 
siderable difference is found to exist in the conformation of the 
abdominal legs of the sexes. Judging from analogy, therefore, 
we may predict that a sexual divergence in these organs exists 
among the Diastylide. On the other hand, as I have found that 
the telson and caudal appendages supply valuable and constant 
specific characters among the Myside, I have chosen these organs 
together with the posterior thoracic feet as the bases of the spe- 
cific character among the Diastylide. It may be thought that 
the descriptions of these parts in this paper are unnecessarily 
prolix, but taking into consideration our present deficiency of 
knowledge respecting these Crustacea, it has been deemed that 
prolixity is a fault on the right side. 
Cyrianassa elegans is easily distinguished from the other forms 
