190 Prof. P. M. Duncan on Liitkenia, 



up the jaw-plate to its upper end, occupying the position of 

 the teeth. The side of the jaws, close to the jaw-plate, is occa- 

 sionally covered with small and close papillae ; and there is a 

 small accessory papilla close to and at the side of the upper- 

 most large ones. The upper part of the jaw beneath the 

 stomach is stout and tumid, and the jaw -plate is large and 

 well developed. 



There are two rounded knobs on the side of the jaw, above 

 the attachment of the mouth-papillge, which are in relation 

 with the upper tentacle ; and the lower tentacle of the angle 

 has five or six short unequal-sized tentacle-scales, forming, 

 with several accessory scales, an obliquely placed curved 

 wedge-shaped mass within the first lower arm-plate and on 

 either side of its oral margin. 



The lower arm-plates, there being six or seven within the 

 disk, are mostly very broad and very short ; further out they 

 are small and triangular, with an aboral projection. They 

 form but a small portion of the lower surface of the arm. 

 The side arm-plates meet below, from the first to the last, 

 giving a broad and comparatively flat under surface. 



The first lower arm-plate is unlike the others in shape, and 

 it is elliptical in outline and much broader than long : the 

 second, longer and very much broader than the first, is some- 

 what rectangular ; its sides are slightly incurved ; and there is 

 a central angular process on the distal and proximal edges, 

 from which there is a reentering curve on either side to the 

 lateral angles of the sides of the plate. 



The third lower arm-plate is very broad, extending across 

 the arm ; it is short, the relation of length to breadth being 

 one to three ; the sides are incurved for the tentacle, and are 

 slightly convex towards their distal angle. There is an 

 angular process or cusp on the broad oral margin, and a 

 smaller one on the aboral 5 and there is a reentering curve on 

 both sides of the processes, giving a very elegant outline. 

 The fourth lower arm-plate is as broad as the third; but 

 it is shorter, and the proximal angular process is more 

 decided than that on the distal edge. The next plate is of 

 the same general shape, but is shorter, and the proximal angle 

 is more pronounced. From this plate to the end of the arm, 

 the others narrow more and more, become angular at the 

 sides and more or less triangular as a whole, and are broader 

 without than within. There is a projection in the median 

 line on the aboral margin, and a reentering curve on either 

 side to the lateral angles ; and the proximal angular process 

 has faintly reentering curves on either side of it. Far out and 

 towards the tip of the arm the lower plates become more 



