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characters undoubtedly. do. often, but not always, hold good. In åa 
L. arctica from Iceland (Fig..7.a).…. I.found: the dentition to be ex- 
actly. intermediate between those of, the two forms. regarded, os nor- 
Fig. 7. ørn bg obtusata. Nat. size. Iceland. 
a' The' variety dretica Møller! 5 Intermédiåte form' between L. obtusåtå f. typica and 
the variety arelten; ec Form with short, obtuse spire. 
mal (Fig. 8a). It agrees with L. obtusata in the above nåmed first 
character (Fig. 8 b), and with L.arctica im the second character 
7 
' 
i 
RER, 
Fig. 8. First lateral tooth of Littorina obtusata. 7/1: 
a The variety aretica. (Fig. 7a) Hamarsfjørdr, Iceland. 5 Forma typica, Vestmannaeyjar. 
ce The variety arctica, Hamarsfjårdr, Iceland. 
(Fig. 8-c). Since it is a. wellknown facet that in the aretic. and b0- 
real zones, forms are often found intermediate between LL. obtusata 
f. typica and L. arctica as. regards the shell, e.g. Fig. 7 b, we are 
lead "to consider L: aretica as va northern variety of L. obtusata. 
The"name Werita littoralis,… Linné, hås caused much" confusion- 
Forbes & Hanley (7), Jeffreys (14); Fischer (16), Tryon (24) ete- 
