NUDIBRANCHS OF THE VANCOUVER REGION l8l 



dibles very large, the masticatory margin smooth. *Radula teeth five in 

 each transverse row, i.e., 2, 1,2. 



Genus Dirona (MacFarland) . 



Dirona MacF. MS., Cockerell and Eliot, Notes on a Collection of Cali- 

 fornian Nudibranchs, Joum. Malacology, 1905, Vol. 12 (3), p. 45. 

 The Brit. Nudibr. Moll., Part VIII (Supplementary), 1910, p. 69. 



Body broad, sub-depressed; head bearing a broad thin veil with 

 smooth, undulating margin, in width equal to, or wider thap, the foot; 

 no oral tentacles ; rhinophores perfoliate, non-retractile within sheaths ; 

 cerata large, inflated, non-caducous, arranged irregularly along margin 

 of dorsum in a closely set series, which extends nearly to median line in 

 front of the rhinophores. Cerata of varying size, the largest usually 

 innermost, with smaller ones external to their bases; cnidosacs absent. 

 Liver lobulated, but with no ramifications to the cerata. Foot broad, 

 roimded in front, tapering behind to a short tail. Anus at the summit 

 of a conspicuous papilla far back, on right side, just below the cerata. 

 Lip disc covered with thick set, hair-like cuticular processes. Mandibles 

 massive, the masticatory surface smooth, formed by a shield-like expan- 

 sion which is reflected over the anterior margin of the mandible. 



Radula narrow, its formula 2, i , 2, the median tooth small, the laterals 

 widely separate from it. First lateral depressed, of moderate size, 

 denticulate on inner face, second lateral large, compressed, simple hamate. 



Dirona albolineata (MacFarland). 



Dirona albolineata MacFarland, Zool. Jahrb., p. 516, pi. 30. 



Body. — The body is smooth and limaciform, bluntly rounded in front 

 and somewhat sharper behind. The slightly convex dorsum bears two 

 series of large inflated lanceolate cetara which are closely set and arranged 

 irregularly along the sides. The inside cerata are the largest and may 

 reach half the length of the animal whereas the outer ones are much 

 smaller. They pass in front of the rhinophores towards the middle line 

 but do not meet while posteriorly they meet in the middle line just in 

 front of the tail. 



Colour. — ^The general ground colour is a beautiful translucent pale 

 whitish grey through which the internal organs can be faintly seen. A 

 dead white line runs round the margin of the veil and along the median 

 crest of the tail. A line of the same colour passes up the inside, over the 

 top and down the outside of the cerata which are slightly flattened 



* MacFarland's diagnosis reads — "Radula teeth in five transverse rows" which is 

 obviously a slip for there are in the two species so far described from 29-35 trans- 

 verse rows five in each row. The necessary alteration has been made. 



