ON THE SHETLAND CRUSTACEA, TUNICATA, ETC. 269 
to the penultimate joint of the peduncle, subquadrate; external margin 
smooth, terminating in a spine; apex obliquely truncate, not extending 
beyond level of the tip of the spine of outer angle; inner margin and 
apex with plumose sete. Mandible palp three-jointed, last two joints 
long, subequal, last slender, both setose. Flattened scalar basal joint of 
pereiopods having a naked external margin, terminating in a spine-like 
point. Last portion of pereiopod multiarticulate ; in last pair articula- 
tions thirteen in number, each with a spine on both margins, and spine- 
like sete on inner margin. Marsupial pouch attached to last pereiopods 
and first pleopods; the latter composed ofa long basal joint (closely resem- 
bling a thigh-bone in form), naked during its length, but having at the 
base a little lobe, bearing four long plumose sete, and having its 
expanded apex surrounded with a circlet of similar long sete, within 
which the two little branches in which the member terminates nestle ; 
these branches one-jointed, terminated by sete; one branch half the 
length of the other. The remaining pleopods, in the formr of a narrow 
scale, furnished with plumose sete. Telson cleft at the apex to about 
one-fifth of its length; sides furnished with 7-9 spines of great size, 
more especially the distal ones, which are equal in length to the cleft; cleft 
margined with rather long, sharp, slender serrations. Inner lamine sub- 
equal in length to (spines of) telson, narrow, fringed with long setx, 
and inner margin also with about ten slender spines ; acoustic organ 
unusually small. External lamine shorter than inner, rounded on 
apex ; outer margin having about twelve greatly developed curved spines 
instead of the usual plumose sete. 
Male.—Themale, instead of having a separate lobe to superior antenne, 
as in Mysis, has the first joint of external filament expanded in a similar 
manner to the female, but is more strongly developed. All the pleopeds 
composed of a large basal joint (in the first furnished with large plumose 
sete, in the others naked) and two branches; first, fourth, and fifth 
pairs with outer branch half as long again as peduncle, multiarticulate 
and setose: inner branch short, with widely diverging plumose sete ; 
second pair with both branches multiarticulate and plumose, the exter- 
nal branch rather more developed than the inner, the latter with a 
small lateral lobe at the base; third pair having outer branch of consi- 
derable length, consisting of four long, rounded, slender, smooth joints, 
the last haying two minute marginal spines, and terminating in two 
slender spines; inner branch shorter than first joint of outer, multiar- 
- ticulate and plumosely setose ; basal joint giving off a small lateral lobe. 
Length three-quarters of an inch. 
Dredged 5-8 miles east of Balta, in 40-50 fathoms; also Banff (Mr. 
Edward), Firth of Clyde (Mr. D. Robertson), and off the mouth of the 
Tees and Norfolk coast (Mr. G. 8. Brady). 
: Genus Nematopus, G. O. Sars. 
Allied to Mysis. Superior antenne having first joint of peduncle with a 
setiferous process on the outer margin; the last joint in male with a hirsute 
lobed appendage. Pereiopods very long and slender, 8-jointed, nearly fili- 
form, with very few hairs, terminating in a well-formed nail. No external 
branchiz. Marsupial pouch as in Mysis. Pleopods in female rudimentary 
as in Mysis, but in male well developed, two-branched ; branches multiar- 
ticulate; the external branch with a setiferous process on its inner margin ; 
in the first pair the terminal part rudimentary, and without sete. Telson 
