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really belonged to the female mentioned by this author. By means of these experiments it was
found that the mature males of this species have almost the same type of shellasthe female; the
male shell differs from that of the female almost only by being somewhat lower posteriorly. —I have
obtained much the same result in the case of two other species belonging to the same group
of forms as A. oblonga, namely A. Grimaldi and A. norvegica. There can scarcely be any doubt
that the males and females which have been grouped together in these two cases really belong
to the same species. The great anatomical resemblances are quite a decided argument for this.
In the case of A. Grimaldi this grouping is confirmed still further by the faet that this male
and female were found together at one locality, where I ascertained by a large number of
dredgings that there were no other males and females of this genus present.
With regard to the type of shell in the males of females that have short, pear-shaped
shells we know practically nothing from the literature that has appeared up to now. G. S. BRADY
and A. M. NORMAN mention, however, 1896, p. 638, that they had found the male of A. teres
(A. M. NORMAN). No description of this male’s shell is given, but the text seems to show that
it was of the same short, pear-shaped type as that of the female. These authors write: „We
are unable to say in what slight respects the shell of the male differs from that of the female.“
Believing it was a female, they had dissected the specimen before investigating the shell more
closely. — I cannot of course say with absolute certainty whether the male and the female that
I have grouped together in this work under the name of A. curta are really the male and female
of the same species. There are, however, strong arguments in favour of the correctness of this
grouping; cf. p. 503. If this grouping is correct, there is thus only rather weak dimorphism
with regard to the shell present in this group of forms as well.
As both males and females of both the elongated and the short type exist, it seems as
if a grouping of males of the one type with females of the other as males and females of the same
species would at any rate necessitate clearer proof than that put forward by G. S. BRADY in
the case of A. oculata A The only argument that seems to support this writer’s assumption is that
the two forms were found in the same sample. „One female only could be found, and this occurred
with only one or two males“, etc. It was thus not a large number of males and females that were
caught together, but only one female and „one or two“ males. This naturally makes this argument
of no value. — Unfortunately this female did not exist in the collection that was sent to me from
the Copenhagen Zoological Museum. It is presumably altogether lost. I am thus unable to confirm
or reject the assumption put forward by G. S. BRADY by making an anatomical investigation.
As has been shown at another place of this treatise, p. 490. G. W. Müller synonymizes
A. oculata with A. teres (A. M. Norman). Whether the female referred by G. S. BRADY to this
species is identical with this species of Norman’s cannot at present be decided with certainty.
It does not seem probable to me. As is shown above, there seems to be still less reason for
assuming that A. oculata, G is identical with A. teres.
In spite of the incompleteness and uncertainty of the original description of this species
two subséquent authors have succeeded, all the same, in identifying with it forms investigated
* Compare p.
the same species.
490 above, G. O. Saks’s explanalion of A. lires and A. Muriae as fema’e and mat’ of
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