Lamellibranchiata. 



Part I. 



Anomiidae. 



Anomia. 



The genus Anomia is represented by 2 species at the Fteroes and Iceland: Anomia sqnaiiinla L. 

 and Anomia patclliformis L. 



As regard the former, I am unable to agree with the prevailing view that A. sqiiamnla. is a 

 variety of A. cphippiuni. The latter is considerably larger and easily distinguished from the fact, that 

 the upper (free) valve of the shell has 3 muscular impressions (one of the adductor, two of the byssus 

 musculature; comp. PL I, fig. 3), whilst the upper valve in A. sqnamula only shows two muscular 

 impressions (one of the adductor, one of the byssus muscle). 



Anomia aculeata IMiiller (PI. I, fig. 2 d) I take to be a variety of A. sqiiamnla, as there are all 

 transitions between smooth and spinous specimens and they agree exactly in other regards, e. g. in the 

 byssus musculature. G. O. Sars has observed correctly in so far that he only found two muscular 

 impressions in the upper valve of A. aailcata and was consequently disinclined to refer A. aculeata 

 as a variety to A.ephippiiim^ where there are three muscular imprints') on the upper valve. But Sars 

 has not noticed at the same time, that ^i. sqnamula also has only two muscular impressions (PL I, 

 fig. 2 c) and consequently cannot be a variety of ^i. cphippiuni either. 



I have sought in vain for the true A. tphippium in my material from the Fseroes and Iceland. 

 Nor have I found this species among the material which has been collected in the course of years in 

 the Danish waters. It is perhaps even doubtful, if A.cphippium occurs at Norway; I do not think it 

 altogether inconceivable that G. O. Sars, starting from the anticipated view that A. squamula is a 

 variety of A.rp/iippitim, has ascribed to A.cpiiippium a distribution in Norway on this erroneous basis 2). 



Again, it is difficult enough to distinguish Anomia pafcliiformis from A. squamula — and prob- 

 ably not always with certaint\-; the upper valve shows only two muscular impressions in both species 

 (comp. PL I, fig. I c with fig. 2 c). The best distinguishing marks are, that the notch in the lower valve 

 is large, almost triangular in A. pafcliiformis (PL I, fig. ib) and the umbo a little way from the margin 

 (PL I, fig. I a), whereas in A. squaviula the notch in the lower valve is small, oval (PL I, fig. 2 b) and 

 the umbo entirely or almost on the margin (PL I, fig. 2 a). 



1) It is not quite fortunate, when Sars describes the adductor imprint as being bi- or tripartite. 



2) Linne also has his two species geographically separated, the main region for A. ephippium being given as the 

 Mediterranean, whilst A. squamula hves "in Oceano Svecico". Sjst Nat. ed. 12, 1, 2, 1767, p. 1150 and 1151. 



I* 



