450 MARPHYSA BELLI. 



whilst a greyish area occurs anteriorly next the latter. A small process projects from 

 each posteriorly. The great dental plates have seven teeth ; the azygos plate on the left 

 has seven or eight teeth ; the curved plate in front about six teeth ; the right anterior 

 curved plate seven or eight teeth. The mandibles (Plate LXV, fig. 11 a) "have black 

 tapering shafts and the cutting anterior edges are sinuous. 



The branchiae commence on the fourteenth foot as a process of ten divisions, all of 

 considerable length, and arising from the outer border of the main stem, the tip of which 

 makes the tenth filament. Sixteen divisions occur on the twentieth foot, nineteen on the 

 twenty-eighth, and thirteen on the last. The filaments are therefore much more numerous 

 than indicated by De Quatrefages, provided the forms are the same, for he gives six to 

 eight as the number of divisions. The total number of branchiae on each side varies from 

 twenty to twenty-five. When the body is stretched the beautiful red branchiae glide 

 alternately, each passing to the opposite side, the right being anterior. In contraction 

 they form a dense group. 



The first foot has a short dorsal cirrus, shaped somewhat like an awl-handle that is, 



constricted at the base, dilating, and again tapering towards the tip. The setigerous 

 region is short and bluntly conical, and is supported by a single blackish spine, or by 

 two or three. It carries four kinds of bristles, viz., dorsally simple tapering bristles, 

 with faint traces of spikes on the edge, and a few brush-shaped forms with nearly equal 

 lateral filaments (Plate LXXXVI, fig. 3*6), then a mixed group of jointed bristles, the 

 majority having slightly curved shafts, dilated and bevelled at the tip, to which a rather 

 narrow bifid terminal piece with wings is articulated, and lastly one or two of the type 

 of Marphysa sanguinea with similar shafts, but with long tapering terminal pieces ending 

 in a fine point. Behind the setigerous lobe is a slightly flattened conical flap, whilst 

 inferiorly is a somewhat thick and broadly conical ventral cirrus. 



The changes which the foot undergoes to the thirteenth consist chiefly in the increase 

 of its various parts. Thus at the eighth foot (Plate LV, fig. 6) the dorsal cirrus is 

 more elongate, the setigerous and the posterior lobes are more prominent, the bristles 

 longer, and the ventral cirrus is longer. These features are still more pronounced at the 

 thirteenth foot, in which the increase in size is considerable. The dorsal cirrus is now 

 long and tapering, the setigerous region of greater depth, the posterior lobe broader 

 (deeper) at the base, and more tapered at the tip, whilst the ventral cirrus or lobe has the 

 shape of a broadly conical flap. The setigerous region is supported by three spines, and 

 bears the elongated slender simple bristles superiorly (Plate LXXXVI, fig. 3), along with 

 certain brush-shaped forms (Plate LXXXVI, fig. 3 b) which have ]ong lateral filaments. 

 Inferiorly are the compound falcate bristles (Plate LXXXVI, fig. 3 a), which are charac- 

 terized by the slight curvature of the shaft and the dilatation of the end, which is spinous 

 at the edges, and by the comparative narrowness of the terminal process, and lastly, those 

 having similar shafts, but with long tapering terminal processes (Plate LXXXVI, fig. 3 c) 

 after the manner of those of Marphysa sanguinea. The posterior lamella of the setigerous 

 region is somewhat lanceolate in front. The ventral cirrus is rather short, massive, and 

 conical. 



The addition of the branchise is the only noteworthy change in the feet of the 

 branchial region, two or three spines being present in the setigerous process. The post- 



