20 Prof. M'liifosli's Xotesfrotn the. 



aiul backward. Tlie tentacles arc iiumerouSj and have the 

 median groove so characteristic of snch oi'gans. Ycntrally 

 the dorsal collar tcrniinatcs, in spirit-preparations, in a short 

 edge. 



The body is enlarged in front, though in the small speci- 

 mens this i.s slightly marked, and tapers to a moderately 

 slender tail, at the tip of which is the anns. The segments 

 vary from forty to fifty-Hve. The dorsal surface is rounded, 

 the ventral with thirteen shields in front, and the median 

 line thereafter is marked by a deep groove. 



The branchi;e are two in nnmber, and vary much according 

 to the age of the specimen, yonng forms having only short 

 stalks Avithout divisions, whereas adults have the branchiae 

 well developed and more or less dichotonionsly divided — with 

 short terminal branches. The anterior gill is the larger. 

 All intermediate forms occnr between the one stage and the 

 other. The best-developed branchite occur in those from 

 deep water, e. g. 80 fathoms off North Unst, Shetland, the 

 lirst pair having a comparatively long stalk before splitting 

 into the terminal tult. The disproportion between this and 

 the second pair is marked, the latter being a short process 

 with only a few divisions. 



On each side are tiftecn bristle-bundles, consisting of 

 translucent bristles with shafts which slightly diminish 

 toward the upper end, where the nariow wings commence 

 and continue on the somewhat long and finely tapered tips 

 lor a considerable distance, disappearing, however, on the 

 hair-like extremity. The tufts diti'er, e. g. from those of 

 Amphitrite fp'cicilis, in being single, no shorter series 

 occurring as in other types. The first bristle-bundle occurs 

 behind the second branehia, and it has no apical appendage, 

 but the two following have on the doisal side of the seti- 

 gerous process, and continuous with it, a lanceolate process 

 like the branehia of Aricia. 



'Jhe hooks present a single tooth aljove the main fang, 

 though in some traces of a second a])pcar in lateral view. 

 The base is somewhat small in proportion to the crown and 

 neck, and its lower edge is evenly convex. The process on 

 the anterior edge curves upward, so as to make a narrow 

 gulf below the great fang, and the edge beneath it is 

 concave. The posterior or dorsal edge has only a slight 

 indentation before joining tiie base. A series of striations 

 pass from the crown down the posterior part of the neck. 



In the widely-distributed Pista cristata, O. F. Miiller, the 

 eleventh species, the cephalic plate has a thick dorsal collar 



