T922. No. 6. NL'DIRRANCHFAl'N'AKN I FlRØHAKSUNnET. 95 



Ae. glauca. (A. iS; H.I Bergh. 



Fig. 55 in text. 



New to the fauna of Norway. Wa.s found in great numbers spawning 

 on the Zostera in the Halangs-poll during July and August 19 19 and 20. 

 hi 1 92 1 it was not to be found in tiie Drobai< Sound. Length up to 50 

 mm. The colour never so red, the cerata never so vermicular and so flat as 

 stated by A. & H. The colour of the liver-processes blueishgrey. The 

 green colour given in A. & H.'s picture of a specimen was never observed 

 in ours. The anatomy of this species was thoroughly examined and was 

 found to accord with previous observations. 



The egg strings were formed to be like long threads wound irregu- 

 laris- round Zostera leaves. The species has never been observed in Norway 

 except at its spawning season. 



Genus 8. Fdvoriniis. Gray. 



Diagnosis of the genus in accordance with Berth's (1882, p. 38I. 



F. albus (A. & H.) Gray and F. bniiichialis IMullerI Bergh, which 

 have previoush' been described as two separate species prove to be varie- 

 ties of one species, which in this work has been called F. albns (A. & H.) 

 Gray. According to the strictest rules of pi'iority the oldest name " F. 

 braiichialis (Muller)" should really have been preserved as the name of 

 the species; my reason for not following this rule is that the white variety 

 F. a/biis is by far the commonest and is found in wider areas, and is 

 therefore more often mentioned in scientific literature than Muller's brown 

 variety „F. braiichialis." A changing of the well known name F. albus 

 might thei'efore cause unnecessary confusion. 



In the Drobak Sound fauna there have been found a whole series ot 

 intermediate colours between that of /•". albus and /". braiuiiialis, and also 

 with regard to morphology no difference can be demonstrated. Thus tlie 

 teeth of the radula ha\e in all specimens been found to be provided with 

 more or less definite denticles \arying in number on each side ot the 

 central cusp. 



During the winter 1919 — 20 the brown \-ariety was strikingly frequent, 

 while in the autumn of 1921 there was a majority of white specimens. 



F. albus. (A. & H.) Gray. 



Syn. F. branrliialis (MOller) Bergh. 



Pl. W. Fig. 16—18. 



The white variety is new to the Kristianiaijord fauna. The brown one, 

 previously described under the name of Acolis braucliialis, was possibly 

 found by Asbjørnsen 1 1854 p. 33). Fairly common. Mature specimens 

 found from 6 to 22 mm. Very varying with regard to colour of the liver 



