NUBIBRAXCHS OF THE VANCOUVER REGION 173 



somewhat paler these colours are retained for some months after preser- 

 vation. 



Dimensions. — The largest specimen measured while living was 39 mm. 

 long by 25 mm. wide by i6 mm. high. 



Head. — The head is very well marked, broad and veliform with a 

 smallish longitudinal slit-like mouth. There is a distinct notch at the 

 front end of the head and the sides of the head are continued out laterally 

 into two large, elongated triangular oral tentacles which curve backwards. 



Foot. — The foot is not very broad, of an elongated oval shape, dis- 

 tinctly concave anteriorly and passing back to a bluntish point. 



Rhinophores. — The rhinophores are retractile into a low sheath with 

 a papillated margin. The rhinophores are directed forwards, outwards 

 and upwards in life and about half their length is formed by a cylindrical 

 stalk. The perfoliate clavus is a long, blunt ended cone bearing 28-30 

 leaves. 



Branchiae. — ^The branchial plumes are nine in number and arranged 

 in the form of a complete circle and are not retractile within a sheath. 

 The low, blunt anal papilla lies in the centre of the circle and is surrounded 

 by numerous papillae similar to those over the rest of the dorsum only, if 

 anything, slightly larger. 



Radula. — The yellow radula is long and nairow and infolded into a 

 deep grove. The rachis is narrow and bare. There are no median teeth 

 and the lateral teeth are 6 or 7 in number and the total number of rows 

 is 35. Of the teeth the innermost is larger and different from the rest. 

 It has a broad almost triangular base much thickened on its inner comer; 

 its antero-lateral comer bears a strong curved spine which although 

 strengthened by a ridge shows no signs of denticulation and projects a 

 good way beyond the laterals; its postero-lateral comer also bears a 

 small but broad triangular tooth-like plate. The first five smaller teeth 

 are roughly triangular in shape with a raised ridge on their outer border, 

 the ridge bearing abo,ut half way along a prominent triangular point. 

 The outermost pleural tooth, apparently not always present, is a much 

 smaller, almost quadrilateral plate. 



The labial armature takes the form of a disc composed of a lafge 

 number of closely packed tiny triangular dejiticles. There is also a 

 ventral curved plate of chitin pointed anteriorly and bifid posteriorly. 

 It is fairly similar to the corresponding structure in A. hudsoni. 



The genital aperture is high up under the mantle on the right side of 

 the body just behind the level of the rhinophores. The penis is fairly 

 long, sub-conical and armed with minute hooks. 



The present species although in general form is somewhat like A. 

 hudsoni but higher and plumper and differently coloured. The branchiae, 



