NUDIBRANCHS OF THE VANCOUVER REGION 1 89 



breadth over the greater part of the length of the clavus. The stout 

 rhinophore sheath bears at the top four tree-Hke processes; of these the 

 an tero- lateral is the smallest and the postero -median much the largest 

 being from two to four times as long as the smallest. At the base the side 

 of the sheath is a dejidriform appendage similarly situated but relatively 

 much coarser than in D. arborescens. From this form the present species 

 can be at once distinguished by the fact that the posterior edge of the 

 rhinophore sheath bears a series of from 3-5 small but well marked 

 dendriform papillae. 



Cerata. — ^The dorsal cerata of this species can be readily distinguished 

 from those of the two preceding species from the much stouter structure 

 of their main stems and this is to be found even in small individuals. 

 They are in all cases la;rge but may be considerably inflated. The 

 terminal branches are quite fine and as noted before of an opaque dark 

 brown or pale chrome yellow. They usually contract considerably on 

 preservation leaving the cerata as stout projections with stout fluffy 

 branches. The first pair of cerata are the largest and lie about f of the 

 way back. The second are slightly smaller and over }4 way back. The 

 distances separating the others diminish fairly regularly and the last 

 pair are quite small and fairly simple. The first three or four pairs arise 

 as practically two main trunks right from the back and each soon sub- 

 divides. The last pairs arise as single trunks. The front two pairs are 

 capable of considerable expansion and may stand up almost half the 

 length of the animal. 



Radula. — The radula is pale yellow in colour, wider than in the two 

 preceding species and has from 35-40 rows of teeth. The median tooth 

 has an oblong base narrow in the transverse direction and bearing a 

 spine. The spine itself has the form of an acute angled triangle with the 

 long sides incurved and bearing a series of from 11-13 well marked fairly 

 large denticles. This tooth is unlike that described for any other member 

 of the genus. The lateraji teeth number from 12-6 on each side of the 

 median tooth. The lateral tooth is a longish rod with a very slightly 

 curved claw-like end that has no sign of latent denticles and is more 

 symmetrical than in other species of Dendronotus. At the outer edge of 

 the radula they become very thin. 



Jaws. — ^The jaws occupy the whole of the side of the bulbus pharyn- 

 geus and are large fairly broad plates of a yellow colour. The crista 

 connectiva is not quite so marked as in th6 preceding species and the 

 superior process is relatively not quite so well developed. The processus 

 mascatorius is stout and bears several small tooth-like projections. 



The penis is long and almost cylindrical. It is often fully extruded 

 upon preservation and exhibits then a series of longitudinal folds. 



