NUDIBRANCHS OF THE VANCOUVER REGION 1 79 



Body. — ^The body is an elongated oval more obtusely rounded in front 

 than behind. The dorsum is flat and continued out as a wide moderately 

 thick mantle. The caruncle is small and inconspicuous. The oral shield 

 is long and large and the lateral corners drawn out into triangular flap- 

 like extensions. The rhinophores are close together at the anterior end 

 and completely retractile within what is practically a common sheath 

 formed by two curved leaves with undulating borders. Beneath the 

 mantle is the usual series of gills. The sides of the body are well marked 

 off from the mantle and foot. 



Colour. — The colour is subject to a considerable amount of variation 

 as Bergh has noticed, he says (3, p. 155) "So wie es einp blase Varietat der 

 typischen Form der P. undulata giebt, kommt auch hier eine helle und 

 eine etwas dunklerer vor". But the two are united by intermediate 

 forms and represent the end forms of a continuous series. The dorsum 

 is of varying shades of warm brown with a number of intense white 

 lines on it. These lines start at the middle and pass outwards at a small 

 angle and all the way down the back the new lines that commence are 

 practically symmetrically arranged. Each white line is single at the 

 beginning but shortly after becomes divided into two by a narrow pale 

 brown band and finally becomes single again at the posterior end. In 

 the middle region there are from 8-10 of these double lines on each side. 

 A similar white line runs around the edge of the mantle, foot and oral 

 hood; the two former remaining spearate at the posterior end. The oral 

 veil, and the rhinophore sheath are of a greyish brown with sometimes 

 a suggestion of reddish brown. The rhinophores themselves are dark 

 grey ^peckled with brown spots afid have thin longitudinal white lines. 

 The sides of the body an4 the foot are of a translucent fawn colour while 

 the gill lamellae are bright orange. Altogether it is a most strikingly 

 coloured animal when alive. 



Dimensions. — The largest individuals measured 48 mm. long by 

 37 mm. broad and 22 mm. high which is considerably bigger than Bergh's 

 largest which was only 20 mm. long. 



Head. — The head is thick and broad continuing out under the veil as 

 a lateral ridge. The mouth is a relatively small longitudinal slit. Some- 

 times in preserved specimens the approximation of the anterior border 

 of the foot and the oral veil almost completely hide the head. 



Foot. — The foot is stout and broad. It is bluntly rounded with ^ 

 median notch anteriorly and passes off behind into a fairly sharp poin 

 which remains quite separate from the mantle beyond which it does not 

 extend. 



Rhinophores. — The rhinophores are short, stout cylindrical and re- 



