3 32 ARWIDSSONIA ZETLANDICA. 



frontal process from which the broad anterolateral flaps pass backward to the pronounced 

 notch, which is confined to the outer half of the flap. Posterolateral margin behind the 

 notches has six larger marginal crenations, each subdivided into two, three, or four minor 

 ones. The very narrow keel arises from the anterior edge of a rounded area a little 

 behind the middle, and posterior to two nearly transverse grooves. It widens as it 

 approaches the median frontal process, and again contracts as it joins it. From each side 

 of the keel posteriorly springs a narrow ridge which ceases ab the enlargement of the 

 keel in front. A deep groove (nuchal groove) lies between the keel and the ridge, and 

 another less pronounced exterior to the ridge. The former debouches on each side of the 

 minute frontal process. Proboscis a globular, grooved mass, with rows of rather long, 

 conical papillae. Body narrowed behind the anterior end, and again increasing toward 

 the eighth segment. Ventral ridge from the first bristled segment to the edge of the 

 caudal funnel. Number of bristled segments unknown. Four unarmed segments 

 posteriorly. Caudal funnel has the shape of a fluted vase, with about forty-four cirri, 

 more or less, alternately long and short, the long being flattened and twenty in number. 

 Anal cone a central button. 



First three bristled segments have long, pale yellow bristles, and two spines with the 

 tip curved. Bristles with stout shafts, tapered tips, and wings, besides translucent, 

 slender forms with greatly elongated hair-like tips and just a trace of wings. Typical 

 hook with a remarkably high crown of six or seven teeth above the main fang, which 

 leaves the neck at less than a right angle, has a slight incurvation of the throat beneath 

 it, and a comparatively short and nearly straight tuft of gular bristles on each side. The 

 neck and shaft are almost of equal length, and the shoulder is marked. Tube of sand, 

 minute fragments of shells, and Foraminifera ; free. 



Synonym. 

 1913. Axiothella zetlandica, Mcintosh. Ann. Nat. Hist., ser. 8, vol. xi, p. 106. 



Habitat. — Dredged by Dr. Gwyn Jeffreys and Canon A. M. Norman in St. Magnus 

 Bay, Shetland, in 100 fathoms in 1867, and in 85 fathoms in the same bay in 1868. 



Cephalic plate (Plate XCIX, figs. 6, 6 a, 6 c and 6 d) slopes downward and is concave 

 rather than convex, has a remarkably wide and somewhat thin margin, and a minute 

 central process in front, the general form of the surface being rounded rather than ovoid. 

 From each side of the minute median process the broad and thin antero-lateral flaps pass 

 backward to the notch, which is, though pronounced, superficial — that is, it is confined to 

 the outer half of the flap and its direction is slightly forward. The postero-lateral margin 

 behind the notches is differentiated by its strise and crenate edge. Six larger marginal 

 crenations are divided into two, three, and four subdivisions. This margin is narrower 

 than the antero-lateral and stands more or less erect, whilst the antero-lateral is pro- 

 cumbent. The very narrow keel arises a little behind the middle, and posterior to two 

 nearly transverse grooves, which run inward from the margin and by a slight enlargement 

 from the anterior edge of a rounded area. It widens as it approaches the median frontal 

 process, and again contracts as it joins it, so that its outline is somewhat clavate, or, if the 

 posterior area is considered, like the gymnastic Indian club. On each side is a long, 



