1 62 Transactions of the Royal Canadian Institute 



other features, the radula and internal organs, etc., that they were simply 

 varieties. The colour disappears very rapidly in alcohol or formalin so 

 that in a day or two no trace of it remains. The plumes in all cases were 

 white and only tipped with pale yellow. One perfectly white specimen 

 was obtained and in this also after preservation the yellow spots in the 

 substance of the mantle showed by transmitted light although not clearly 

 visible externally. Its radula and internal anatomy showed it to be a 

 typical C. marginata. 



Dimensions. — The largest specimen measured in the living condition 

 was 33 mm. long, 17 mm. broad, and 6 mm. wide. 



Head. — ^The head is small with a longitudinal slit-like mouth The 

 short flattened triangular tentacles bear a groove on their postero- 

 external border. 



Foot.— -The. foot is quite narrow and elongated and as noted before 

 has a pale yellow line around the margin save in front. Anteriorly it is 

 abruptly rounded and divided into two lips, the lower thick and the upper 

 thin and bearing a median notch. 



Khinophores. — The rhinophores incline backwards and are com- 

 pletely retractile into a shallow sheath with a tuberculate margin. The 

 stalk is short and the perfoliate clavus subconical, bearing 16-18 leaves. 



Branchiae. — ^The six bi-pinnate branchial plumes are arranged in an 

 almost complete circle and are retractile into a shallow sheath with a 

 tuberculate margin The anal papilla completes the gill circle and is 

 fairly well marked while the renal opening is small and inconspicuous. 



Radula. — The pale radula is about half as broad as long with a 

 shallow median groove. The teeth lie in about 90 rows of about 50 lateral 

 teeth on each side of a median tooth. This median tooth is broadish and 

 the end turned over finishing with 4 or 5 serrulations. The first lateral 

 teeth are somewhat similar save that they have also a short curved spine 

 directed inwards as well as the serrulations. Passing outwards in the row 

 the spine becomes more marked and has sharper serrulations but on one 

 side only, finally the extreme lateral teeth are approximately triangular 

 with one denticulate edge. 



The short glans penis is sub-conical and bears minute hooks. 



This species was first described by MacFarland (10) 1095 and again 

 more fully (11) later in the same year, when he gave a description of the 

 internal anatomy to which I have nothing to add. 



Habitat. — ^This form is not so common as the preceding ones but is 

 not rare during the months of April, May and June. It has been taken 

 from Jesse Island, Brandon Island, Mudge Island and two small speci- 

 mens were dredged from the Fairway Channel near Gabriola Island 

 (Station 4). 



