ARWIDSSONIA ZETLANDICA. 331 



tapered tip. A few slender, hair-like forms occur at the base, and represent the second 

 group. The hooks (Plate CVIII, figs. 9 and 11) somewhat resemble those of Prcmllella 

 prmtermissa, but the crown is more elevated and the great fang is shorter, whilst all that 

 represents the gular bristles is in some a short process beneath the great fang, which does 

 not reach its tip. As a rule, six teeth occur above the great fang. Another peculiarity 

 is the absence of striae in the anterior region of the neck down to the shoulder. 



5. Pbaxillella V. 



A form dredged off Cape Guardia in the ' Porcupine ' Expedition of 1870 is 

 characterised by the peculiarly notched cephalic rim (Plate C, fig. 20). In lateral view a 

 large flap occurs in front, separated posteriorly by a notch from the posterior half, which 

 is composed of three smaller segments and a larger posterior one, the hind edge of which 

 abuts on the deep and broad median posterior notch. On the other side (left) the hind 

 segment of the rim is larger, so that only two smaller ones occur between it and the edge 

 of the long anterior division. A short, conical peak is present anteriorly in the middle 

 line, and in front view the large anterior flaps or lamellae of the rim are prominent, more 

 so than in the Praxillella prxtermissa. The cephalic plate has a median ridge and nuchal 

 grooves like those of P. prsetermissa. Bold anterior belts of glands are present, the first 

 distinct one being that (a narrow one) between the third and fourth bristled segments. 

 Broader belts are at the anterior border of the fifth, sixth, seventh, and eighth segments. 

 The hooks somewhat resemble those of P. prsetermissa, but the crown appears to be 

 higher, five teeth occurring above the large fang. The gular bristles spring close to the 

 latter and pass on each side of it. They are proportionally short. 



Arwidsson arranges the Axiothella group according to the condition of the skin- 

 glands, the presence or absence of a ring next the anal cup, the presence of a collar, the 

 nature of the anal cirri, and the hooks in the anterior segments. His genera are 

 Axiothella, Clymenella, and Euclymene. The following genus differs in certain respects, 

 but may for the present be placed with these. 



Genus CXXIII. — Abwjdssonia, n. g. 



Cephalic shield rounded, concave, with wide and thin margin; a minute median 

 frontal process. Postero-lateral region of the margin notched. Keel arises from a 

 rounded area a little behind the middle of the plate, posterior to nuchal grooves. 

 Proboscis with long conical papillae. Four unarmed segments posteriorly. Caudal funnel 

 a fluted vase with numerous cirri, which are alternately long and short. Anal cone in 

 centre. First three bristled segments have bristles and spines. Hooks with high crowns. 

 Tube free, of fragments of various kinds of sand, and shell-fragments. 



1. Arwidssonia zetlandioa, Mcintosh, 1913. Plate XCIX, figs. 6 to 6/— head and tail; 

 Plate CX, figs. 5 to 5 d — bristles, spines, and hook. 

 Specific Characters. — Outline of cephalic shield rounded rather than ovoid, concave 

 rather than convex, with a remarkably wide and rather thin margin, and a minute central 



