NUDIBRANCHS OF THE VANCOUVER REGION 1 55 



equally rounded. The dorsum is arched but not markedly so and covered 

 with low bluntly conical tubercles of varying sizes. The mantle is thick 

 and extends well beyond the foot all round save that in active crawling 

 the tail end of the foot may protrude for a short distance. 



Colour. — The general ground colour is a dusky yellow cind the dorsum 

 is covered with brownish or black patches irregularly arranged. The 

 animal can readily be recognized from the illustration given by MacFar- 

 land (Fig. 4, pi. XXIII), but in the specimens I have seen alive, amount- 

 ing to over 100, the spots have been relatively not so large but more 

 numerous; however they are subject to considerable variation. The 

 colour disappears quickly in spirit or formalin save for the spots which 

 persist some long time. 



Dimensions.— The largest specimen examined measured; length 

 48 mm., breadth 24 mm., height 12 mm. 



Head. — The head is small with a small vertical slit like mouth. Its 

 sides bear short, blunt, fold like, auriculate tentacles which are grooved 

 on their postero-extemal margin. 



Foot. — The foot is also eliptical but narrower than the body; it is 

 without a median notch ; the anterior margin bilabiate with the upper lip 

 wider and thicker than the lower. 



RhinopJiores. — The rhinophores are fully retractile into deep sheaths 

 with a tuberculate margin. The clavus is borne upon a slightly conical 

 stalk; it is somewhat dilated, sub-conical, perfoliate having 24-30 leaves 

 on each side. 



Branchiae. — The seven branchial plumes are 3-4 pinnate and spread- 

 ing and can be completely withdrawn into a deep sheath with a tuber- 

 culate margin. They are of a dusky yellow or brown colour almost 

 always darker than the body colour and arranged in a broad horseshoe 

 shape around the truncated, conical anal papilla. The renal opening is 

 just anterior to the anal papilla on the right side. 



Radula. — The radula is pale, deeply grooved, short and broad. The 

 teeth are arranged in 30-33 rows. The rachis is narrow and naked. The 

 pleural teeth vary from about 42 anteriorly to 50 posteriorly, are strongly 

 hooked and compressed. The largest teeth are near the middle of the 

 row and they decrease in size inwards and more rapidly outwards. 



The glans penis is unarm.ed and when everted conical, long and 

 slender. 



This species was first described by Cooper (5) in 1863 and dried 

 specimens were obtained by Bergh (2) from Sitka, Alaska. Cockerel 

 and Eliot (4) describe three small specimens from La Jolla in Southern 

 California. The first full account has been given by MacFarland (10,11) 

 who describes fairly completely the internal anatomy of this form. It 



