134 PROCEEDINGS OP THE MALACOLOGICAL SOCIETY. 



for several reasons. The same author criticizes Eschscholtz's 

 account of the species, and concludes, " Evidentemente, la figura 

 di Eschscholtz e falsa, e deve percio essere eliminata dal materiale 

 scientifico." This sweeping statement is hardly necessary, and, 

 as will be pointed out below, the description furnished by 

 Eschscholtz was the most complete in some respects that was given 

 for seventy years. 



In 1862 Cooper (5, p. 205) described a species ^olis {Flahellina) 

 opalescens with an opaline colour on the dorsal tentacles and an 

 orange stripe between them (cf. Eschscholtz). Again, in 1863 

 (6, p. 60), the same author also records this species as Flahellina 

 opalescens, mentioning a pale variety with white tipped branchiae 

 {i.e. cerata). 



Bergh in 1878 (1, p. 573), and again in 1879 (2, p. 81), formed a 

 new genus Hermissenda for this species. It is closely allied to 

 Phidiana, but differs in the produced angles of the foot, the form of 

 the teeth, but especially in the absence of a hook on the penis, and 

 in these papers he identifies the Molis or Flahellina opalescens of 

 Cooper as Hermissenda ojmlescens, the only member of the genus. 

 The rhinophores are stated to be yellow with an orange stripe between 

 them (cf. Eschscholtz). The papillae are yellow with the purple red 

 liver diverticulum shining through. 



Cockerell in 1901 (3, p. 122) also described the same form, calling 

 attention to the two " opal blue " lines on the back forming 

 practically one, but dividing on the head and just behind it to admit 

 " a bright orange streak ". He also mentions the " broad orange 

 stripe on each side of the head ", the fact that the cerata possess an 

 " orange subterminal ring ", and that they are " easily deciduous " 

 {cf. Eschscholtz). 



The same author in conjunction with Eliot in 1905 (4, p. 50), 

 but strangely enough without reference to his previous paper, again 

 dealt with this species. This paper also mentions the " opalescent 

 stripe down the back, bifurcating anteriorly so as to include an 

 oblong area of bright orange ". 



The first full account of the coloration of this species was 

 furnished by O'Donoghue in 1921 (9, pp. 201, 202), but at the time 

 the paper was written the author had overlooked Cockerell's paper 

 of 1901 for the reason given above, and had not access to 

 Eschscholtz's atlas. A second paper by the same author (10) deals 

 with the range of colour variation met with in the same species. In 

 the two papers practically every point in regard to colour mentioned 

 by Eschscholtz is also described : the opalescent line along the 

 back bifurcating at the front to include a bright orange area and 

 then passing on to the oral tentacles ; the orange area on each side 

 of the head and neck ; the light-coloured opalescent line below this 

 area ; the iiiterior of the cerata may be almost black, and they have 

 a white line on their outer border ; the cerata in the dark varieties 



