i8o Transactions of the Royal Canadian Institute 



tractile within a common sheath. The rounded tips are smooth but just 

 below are a series of shallow longitudinal folds. 



Branchiae. — The branchiae lie on the under surface of the mantle 

 forming a series of about 20 large and some smaller obliquely transverse 

 gill plates. Each plate bears a series of about 30 thick side lamellae. 



Radiila. — The pale yellow radula is broad and contains from 22-32 

 rows of teeth. These consist of a median tooth and a series of lateral 

 teeth reaching the number of about 46 on each side. The base of the 

 median tooth is quadrangular with its anjterior corners slightly produced 

 into points. It bears a median spine with two pairs of small lateral 

 spines and a series of 3 or 4 lateral denticles. The first lateral tooth has 

 a triangular or polygonal base and bears a short claw like spine which 

 is slightly serrulate on its outer side. The next lateral tooth is simple or 

 claw-like. The succeeding laterals have also a side spine which may be 

 double as well as the main one giving a characteristic bifid appearance 

 and finally the outermost are simple long narrow plates. 



Jaws. — The jaws are well developed each consisting of a curved leaf 

 slightly hollowed on the posterior side. The crista connectiva is practi- 

 cally a straight smooth edge. The stout cutting border of the mandible 

 is smooth and produced into a longish process on each side which is free 

 from the remaining portion of the mandibular plate. 



The tubular anal cone is situated more than half way back in the 

 middle of the right side of the body beneath the mantle. The genital 

 opening is latge and lies on the right side just behind the flap-like ex- 

 tension of the oral veil. 



The penis is fairly long, stout and sub-conical. 



This species was first described by Cooper (5) and subsequently by 

 Bergh (3) who gives a good account of its internal anatomy. 



Habitat. — This is a common, wide spread species although nowhere 

 plentiful. It has been dredged in Hecate Strait, between Gabriola and 

 Snake Islands (Station 48), Pylades channel, and China Hat, in from 

 15-35 fathoms. 



Family Dironidae (MacFarland). 



Body aeolidiform, the foot wide, rounded in front, the tail pointed; 

 oral tentacles absent; head with a large veil; cerata without cnidosacs, 

 closely arranged along the sides of the dorsum and extending forward 

 towards the median line in front of the rhinophores. Liver lobulate, 

 without branches extending into the cerata; rhinophores perfoliate, 

 without sheaths; anus on right side near posterior end of body. Man- 



