50 N. ODHNER, NORTHERN AND ARCTIC INVERTEBRATES. VI. PROSOBRANCHIA. 2 SEMIPROBOSCIDIFERA. 



ticula still retains its original shape from whicli tlie dimensions given above are obtained. 

 From the measurements the agreement of the sliell witli L. latens is evident. The iden- 

 tity is proved, too, by the figin-e given by Forbes & Hanley (Pl. XCIX, Fig. 10), repre- 

 senting a view of the shell from the aperture and exactly resembling the photograph 

 (Pl. 1, Fig. 6) of the present work. 



The coloiiration of the animal gives vaguer characters for identifying L. tentacu- 

 lata. MoNTAGU (1811) describes the colour in the following words (P. 186): »The 

 superior lamina is yellowish, sprinkled with bright brimstone colour and marked with 

 round pustules interspersed with a few black spöts». — »A variety is destitute of the 

 black spöts and the yellowish are more conspicuous. » 



This colouration reminds one of that of L. latens, given by G, O. Särs (1878) and 

 Bergh (1886); the last-named aiithor says in the diagnosis (P. 168): »Color paginae 

 superioris brunneus, fuscato sparsim maculatus; paginae inferioris albescens. » Loven 

 (1846) speaks of the colour of L. tentaculata as follows (P. 147): »Pallium depressum, 

 subverrucosum, fulvum, rufo pictum». According to G. O. Särs (1878) the mantle is 

 almost smooth (»pallio sublsevi»). 



A contrast to this colouration is that of L. perspicua in the following description by 

 LovÉN (1846): »pallium tuberculosum, cinereum, nigro striolatum, fulvo maculatum». 

 But MoNTAGU (1803) describes it as a »reddish or brown colour, sometimes nearly white» 

 (P. 212). On the supposition that Montagu in his »Bulla haliotoidea» does not in- 

 clude the two forms together, but only refers to L. perspicua, this species must vary 

 coiisiderably in colour. 



Tliough LovÉN describes the colour of L. tentaculata in about the same manner 

 as MoNTAGU, his shell is not identical with Montagu's type (= L, latens Muller), For 

 he says: »Testa priori (= L, perspicua) simillima, subopaca, striis evanidis». The figures 

 in the present work (Pl. 1, Figs. 2, 3) show the greatest resemblance to L. perspicua, 

 though the body-whorl may be more flattened, a character of little importance and one 

 subject to variation. It has a less number of whorls than the adult specimens of L. per- 

 spicua and is consequently merely a young specimen of this species. 



Jeffreys (1867) includes in L. perspicua Montagu's L. tentaculata, which he con- 

 siders as the male, while Montagu's Bulla haliotoidea he supposes to be the female. On 

 P. 238 Jeffreys states that »the types of both Montagu's species are in the British 

 Museum, and represent the two sexual forms. The male is the Marsenia complanata 

 of Leach, the female his M. producta». Jeffreys' view about the sexual dimorphism 

 is quite wrong. The depressed L. tentaculata consists of both sexes; of the specimens 

 from Cullercoats, preserved in the State Museum, 2 are males and 1 a female. Of the 

 higher form, M. producta Leach (= L. perspicua Linné), the females are more commou 

 than the males; tlius among 25 specimens collected by Loven in Gullmarn, 20 were 

 females, and of 35 specimens, collected by Asklund in 1888 at Skar, 26 were females. In 

 the general form of the shell the sexes of L. perspicua cannot be distinguished from 

 each other. 



From the radula no distinguishing characters for L. perspicua and L. latens are ob- 

 tainable. The median tootli varies in both species in the same manner. Bergh (1886) 



