954 DR. H. J. HANSEN ON CRUSTACEANS [Dee. 1, 
specimens, the one determined by Chun, the other by Ortmann, are 
referred by these authors to the same species. 
S. cornutus, Kr., and especially S. longispinus, Bate, present 
some affinity to S. edwardsi, Kr., and allied species, which becomes 
very evident by the fact that a short process is found on the outer 
side of the third joint of trl.’ and trl.’ 
Of S. inous, Fax., I have seen no specimens. 
A.b. 8.1. Of S. robustus, Smith, S. japonicus, Bate (S. mollis, 
Smith), and S. bisulcatus, Wood-Mas., I have seen no specimens. 
Of S. robustus we possess several stages of the Mastigopus, but 
having found none of them described I will omit discussing them 
in this paper. 
A.6, 3.2. This rich section of adults and larve I have called 
the arcticus-group, as they-are very nearly related to each other, and 
S. arcticus, Kr., is the only one well described of the mature forms 
and the sole species of which I am able to trace the whole develop- 
ment from the Acanthosoma (incl.) to the adult. I will begin with 
some remarks on the adults and on a subadult species. 
S. areticus, Kr., is well represented by Kréyer (p. 240, tab. iii. 
fig. 7, a-g; tab. v. fig. 16); later on S. I. Smith, in the various 
papers (see above), communicates some additional notes and good 
figures. The species has been captured in the Atlantic, northward 
to Greenland, and southward to lat. 38° S., long. 12° E. (Mus. 
Copenh.) ; further, in the Mediterranean near Ischia (S. magnificus, 
Chun), and some older larve in the Adriatic at Ragusa and 
Lesina (Chun’s collection), But, together with these last larve, I 
found in Chun’s collection some young specimens and older larve 
of a new and unfortunately closely related species, S. mediterra- 
neus, n. sp., Which makes it necessary to present some remarks on 
the two species, so that it will be possible to distinguish them 
from each other. Previously no valid species allied to S. areticus, 
Kr., was known from the Atlantic or the Mediterranean. 
The largest specimen of S. mediterraneus, m., is 19°5 mm. long, 
and has almost assumed the adult shape, but the eyes are still not 
black and therefore their final magnitude cannot be determined. 
Of characters between this subadult stage and the subadult and 
adult S. arcticus, Kr.,I have found the following :—S. mediterra- 
neus is destitute of the hepatic spines and the gastro-hepatic 
groove ; the supra-ocular spines are quite rudimentary ; the basal 
joint of the antenn. peduncle is obviously somewhat shorter than 
the two following taken together, which are a little more coarse 
than in S. areticus, while the basal joint from the spine near the 
basis of the exterior margin is somewhat more narrow, with the 
exterior margin less convex in outline than in S. areticus; the ext. 
br. of urp. is but 4 times longer than broad, with the outer margin 
beyond the spine strikingly concave. In S. arcticus, Kr., the 
supra-ocular and hepatic spines and the gastro-hepatic groove are 
well developed; the basal joint of the antenn. ped. is (measured 
with accuracy) almost or quite as long as the two following taken 
together; the ext. br. of urp. is exactly 5 times longer than 
