152 Transactions of the Royal Canadian Institute 



and alternate in size. The larger ones are directed upwards partly over 

 the back and the smaller ones point laterally and slightly downwards. 



Radida. — 'The radula is strong and broad and bears from 38-42 rows 

 of teeth. Bergh gives the total number as 73. The lateral teeth in the 

 widest part of the tongue number from 58-60 on each side. The median 

 tooth is broad and possesses 3 cusps which are however fairly short. 

 The first lateral teeth are elongated and triangular and quite different 

 in shape from the remainder. The remaining laterals are claw shaped 

 getting longer and more slender as they pass outwards. 



Jaws. — 'The jaws are yellow in the outer parts and a deeper brownish 

 colour along the cutting edge. They are in the form of two curved 

 longish oval plates with the cristae connectivae well developed and 

 joined by a tough connective tissue. The cutting edge is strong and 

 continued back as two fairly long processes which are free from the 

 lateral plate. Over the major portion of its length and along the ex- 

 tensions, the edge is provided with a number of closely fitting polygonal 

 plates many of which bear pointed denticles. The other plates without 

 the denticular points are much smaller and form a sort of smooth pave- 

 ment. The penis is short and sub-conical. 



This species was first described by Bergh (3) from specimens obtained 

 from Shumagin Bay, Alaska, and from off the coast of California. This 

 author gives a good account of the internal anatomy. 



Habitat. — The one specimen examined was dredged in 15-25 fathoms 

 in the entrance of the channel between Jesse and Newcastle Islands. 



Tritonia exsulans Bergh. 

 Tritonia exsulans Bergh. Bull. Mus. Comp. Zool., Harvard, Vol. XXY, 

 1894. p. 150. 

 Body. — The general body form is a broad oval with a pointed pos- 

 terior end. The dorsum is fairly flat and irregular; it is highest about 

 the middle and slopes off more sharply behind than in front. Along 

 each side of the dorsum is a low ridge bearing from 16-19 small branched 

 gill tufts and marking it off sharply from the sides which slope rapidly 

 downwards and outwards to the edge of the broad foot. The large 

 rhinophore sheaths lie just antero-median of the first gill tuft. The veil 

 is strongly developed but not projecting far and well notched in the 

 middle line; on each side it bears a series of 12-14 small conical papillae 

 and on the ventral side at the lateral edge a broad, short, grooved 

 tentacle. The short anal papilla lies about half way back on the right 

 side of the body below the line of the branchial tufts. Above it is the 

 renal pore. The genital aperture is situated on the same side as and 

 below the anal papilla not quite half way between it and the level of the 

 rhinophores. 



