I70 Transactions of the Royal Canadian Institute 



AcANTHODORis HUDSONi (Mac Far land). 



Acanihodoris hudsoni MacFarland, Proc. Biol. Soc, Washington, 

 Vol. XVIII, 1905, p. 51; Bull. Bur. Fisheries, Washington, XXV, 

 1906, p. 144. 



Body. — The body is plump and well arched, almost ova) but slightly 

 broader in front than behind. The mantle is fairly thick and wide and 

 sharply marked off from the foot which it completely overlaps every- 

 where save at the posterior end during locomotion. The dorsum is 

 covered with fine closely set conical papillae which are not retractile 

 anfd give the animal a characteristic appearance usually easily seen in 

 preserved specimens. 



Colour. — The colour of the few specimens I have seen alive has been 

 a translucent white with the clavus of the rhinophores the ends of the 

 gills and the mantle edge of a pale lemon yellow. The yellow in one 

 specimen was hardly discemable. 



Dimensions. — MacFarland records the animal as reaching 35 mm. 

 long, 22 mm. broad and 9 mm. high, but the largest I have measured was 

 30 mm. long, 19 mm. broad and 7.5 mm. high. 



Head. — The head is veliform and quite broad passing out laterally 

 into the two triangular oral tentacles. There is a notch at the front end 

 of the head. The mouth is a small longitudinal slit. 



Foot.— The foot is broad and oval rounded, slightly concave ante- 

 riorly a;nd a little more pointed posteriorly. 



Rhinophores. — The rhinophores are tapering, somewhat conical and 

 directed slightly forwards and outwards in life. The perfoliate clavus 

 bears about 22-24 leave^ and is about half the total length of the rhino- 

 phores. It is retractile into a shallow sheath with a papillate margin. 



Branchiae.— The branchial plumes are five in number and not re- 

 tractile within a sheath. They lie in a complete circle enclosing the anal 

 papilla, which is low and blunt, and other papillae similar to those of the 

 general surface of the dorsum. 



Radula. — The radula is quite narrow, folded to form a deep gutter, 

 and with a narrow naked rachis. The pleural teeth are 7 or 8 in number, 

 the innermost being large and the laterals much smaller. The large 

 tooth has a quadrangular base and bears a strong slightly curved spine, 

 on the inner margin of which are a series of tiny denticles 5-7 in number. 

 The small pleural teeth are somewhat triangular in shape with a raised 

 edge and they get slenderer as they pass outwards ; the first and largest 

 lies un(der the base of the large tooth. The spine of the large tooth only 

 extends a short way beyond the lateral teeth. 



The mouth is armed with a labial disc pale yellow in colour. The 



