450 



PROF. P. M. DUNCAN ON SOME 



and bounds tlie generative slit. Tlie side moutli-sliields are large 

 and oblique, rather broad, and are united at their inner edge, 

 which is produced between the jaws ; the aboral edge is in contact 

 with the angular process of the mouth-shield. 



The jaws somewhat resemble the side mouth-shields in shape ; 

 they are short, wide apart without, are united within, and are 

 rather projecting downwards. The mouth-papillae are broad, short 

 and close, and the innermost o£ each augle is small and diamond- 

 shaped. The others, equal in height, form a linear surface, which 

 is continuous, and the separation of the papillae is only indicated 

 by faint line. The outermost is the broadest, and there are in 

 all eleven to each angle including that at the apex. 



The outer end of each jaw reaches to the opening for the ten- 

 tacle, or to the side of the first lower arm-plate. 



The lower arm-plates. — All are separate, from the union of the 

 side-plates in the median line. The first, although differing in 

 shape from the others next in succession, is as large as they are ; 

 it is very peculiar in shape, being something like that of the blade 

 of a hatchet. The margin within is narrow and notched, the 

 outermost teeth fitting therein. The sides are re-enteringly 

 curved, and within they bound the tentacle-opening and sup- 

 port three close, short tentacle-scales, and without they expand, 

 where the plate becomes broad at its distal end, which is broadly 

 curved, with rounded edges. 



The next plate is broader than long, angular within, curved 

 without slightly ; and the sides, in one part rather straight, become 

 curved where the side-plate passes obliquely to join its fellow 

 along the median line. The third lower arm-plate is not so broad 

 as the second, and has the same general shape. At about the 

 twelfth or thirteenth lower arm-plate the size is much diminished, 

 and the plate ceases to be recognized at about the twentieth joint, 

 which is close to the tip. 



The side arm-plates unite below along the median line and 

 separate the first lower arm -plate from the second, and the second 

 from the third very definitely ; and from this point the length 

 of the junction increases, and is greater than the length of the 

 lower arm-plate. !Ftrrther down, the side arm-plates nearly form 

 the whole of the joints ; they are broad and spread out wider with- 

 out than within. A small, short, subspiniform tentacle-scale is 

 on each side-j)late, just external to the side of the lower arm- 

 plate ; its direction is longitudinal, and it protects a long, slender 



