o'donoghue : nudibranchiate mollusca. 135 



have a deep orange tip ; the two lateral light lines in the tail region 

 and the light opalescent line along the margin of the foot. 



These points are taken from O'Donoghue and arranged in the 

 order in which they are dealt with by Eschscholtz, and I think it 

 will be obvious at once that such a closeness of description makes it 

 certain that the same species is under consideration in both cases. 

 If only the intervening observers had given a more precise account 

 of the colour of the living animal 1 think the identity of Gavolina 

 crassicornis and Hermissenda opalescens woald have been established 

 earlier. Examination of the radula shows that Bergh, Cockerell 

 and Eliot, and O'Donoghue were all dealing with the same species. 

 The name ojmlescens, therefore, must be discarded in spite of its 

 familiarity and of the fact that it describes the characteristic 

 opalescent appearance of the lines of this beautiful species so well, 

 and the nanie crassicornis substituted for it. 



The classification and synonymy of this form is therefore as 

 follows : — 



Family ^OLIDID.E, Eliot, 1910. 

 Genus Hermissenda, Bergh, 1878. 



Species Hermissenda crassicornis, Eschscholtz, 1831. 

 Synonymy : Cavolina crassicornis, Eschscholtz, 1831. 



Facelina (Cavolina) crassicornis, Gray, 1857. 

 Molis (Flabellina) opalescens. Cooper, 1862. 

 Flabellina opalescens, Cooper, 1863. 

 Hermissenda opalescens, Bergh, 1878, 1879. 

 Facelina (Cavolina) crassicornis, Trinchese, 1881. 

 Hermissenda opalescens, Cockerell, 1901. 



Cockerell & Eliot, 1905. 

 O'Donoghue, 1921, 1922. 

 „ ,, O'Donoghue & 



O'Donoghue, 1922. 



B. Cavolina suhrosacea. 



This was the third of the Alaskan forms described by Eschscholtz, 

 and was also found on Sitka Island. The figure of this species is 

 poor and the description very brief. From this account it is only 

 necessary to quote the following points : " Die vordern Fiihler 

 fein " (i.e. oral tentacles) — " die hintern Fiihler sehr schwach 

 geringelt " (i.e. the rhinophores) — " das vorderer Ende der Fussplatte 

 ist jederseits mit einem fliigel-artigen anhange versehen." 



The original genus Cavolina, Cuvier, comprised forms with non- 

 perfoliate rhinophores and rounded angles on the foot, so that this 

 species was not accurately referred to the genus by Eschscholtz. 

 Gray (8) included this with the foregoing species in the genus 

 Facelina, and in the same way Trinchese (13, p. 31) pointed out 

 " Nemmeno la Cavolina suhrosacea di Eschscholtz deve essere 



