526 AKE NORDENSTAM 
same year two additional members of Anatanazs were described: 7. spongicola 
Barnard and 7. Ohini Stebbing. In 1919 STEBBING added another species, 
T. Nierstraszi. he subgeneric position of 7. Gayz Nicolet (1849) remains un- 
decided, the number of free abdominal segments beeing unknown. 
One of the new species of 7azazs which I propose to describe, 7. “neatus, 
is remarkable for the sexual difference which is apparent even in immature 
individuals. As mentioned before, no adult specimens are present, but there 
are two kinds of young individuals, one (probably the females) more narrow, 
almost cylindrical, with the thoracic segments longer and the ventral side con- 
vex, the other (probably the males) broader, with the thoracic segments shorter 
and the ventral side flat. The pairs of antennae, the mouth-parts, and the legs, 
(also the chelipeds) agree very well in both kinds. In a great many other 
genera (cf. HANSEN 1913) the same sexual difference is the rule, but it has 
not before been recorded from the genus Z/anais. 
Many species of 7anazs are not very well known, This is especially the 
case with the more common young individuals, which are very similar to each 
other in different species (cf. HANSEN 1913, VANHOFFEN 1914). The legs and 
mouth-parts have but rarely been fully described but may certainly show 
differences in all species, also in immature individuals. In conformity with 
this opinion and emphasizing the importance of describing even immature 
specimens, I have thought it worth while to deal with the present small amount 
of material also, though at least 4 previously described species are so similar 
or so imperfectly known that there is a possibility of their being identical. 
These species are: 7. gracilis Heller, Normani Richardson, spongzco/a Barnard 
and Ohlint Stebbing. 7. macrocheles Nicolet, which has the anterior border 
of the carapax truncate, may be a different species — perhaps as VANHOFFEN 
(1914) supposes a collective form. 
Tanais (Avatanais) marmoratus n. sp. — PI. 20, fig. 1; text figs. I, 2. 
Subadult male (length 5 mm) and immature specimen (length 2.5 mm). 
Loc. Juan Fernandez: Masatierra, on a buoy in Cumberland Bay. 
Description. 
Body with a length of about 5 times the width, laterally with a few setae. 
Carapax, seen from above, with the lateral margins convex to about half 
of its length (in the immature specimen evenly convex), anterior border about 
half as broad as posterior. Frontal margin between the eyes triangulate. Eyes 
well developed, of about 6 ocelli, on conical peduncles, which are situated in 
small cavities. 
Thoracic segments with the lateral margins rounded. Ventral side slightly 
vaulted, in the immature individual almost flat. Coxal plates on the first free 
thoracic segment produced forwards and acute. The 5th and 6th thoracic 
segments are the longest ones. 
Abdomen a little longer than the last two thoracic segments together. 
Last abdominal segment with the posterior margin rounded and about as long 
as the 4th and sth together. The first 3 abdominal segments with setae in their 
lateral margins. 
