526 TAGE SKOGSBERG 



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 shell as the 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 fact 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 imder 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.* 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 foimd, 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. MULLER 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, ^ is identical with A. teres. 



In spite of the incompleteness and uncertainty of the original description of this species 

 two sul)s<'i|uent authors have succeeded, all the same, in identifying with it forms investigated 



* Coinpan' p. Vm ;ilj<jvr. (i. O. Sahs's explaiialioii ol' A. teres and A. Mai-iue a.s lonia'c and mali' of 

 the Same si)ei'ies. 



