60 PBTTA PUSILLA. 



From the second cirrus a ridge passes as in other forms ventrally on each side. In 

 this species the anterior margin is 4 — 5-dentate, whilst in the centre is a deep hiatus. 

 In small examples the processes are slender tapering papillae. The branchiae on the next 

 two segments are typical. Large cement-glands, homologous with those of Lagis Koreni, 

 occur in the fifth and sixth segments. The duct opens behind the second branchia and 

 the first bristle-tuft. No muscle is present (Hessle). 



The second region corresponds with that in other forms, viz., has more slender 

 bristles in smaller tufts than the succeeding. Their structure, however, corresponds 

 with the type common to all, including the posterior series (Plate CXXV, figs. 7 — 7 c). 

 The stout simple bristles are tapered distally and have traces of wings (fig. 7 a). The 

 others have a spear-head enlargement at the end of the shaft and a tapering tip (fig. 7 b), 

 but the enlargement is proportionally broader and the tapered tip shorter than in allied 

 forms. In the posterior region the fourteen pairs of bristle-bundles exhibit a gradation 

 from the anterior to the posterior extremity. Moreover the region is only a little tapered 

 posteriorly, the termination being comparatively broad. In consequence the caudal 

 appendix projects little ventrally from the truncated end of the body, the last foot being 

 modified into a rounded flattened lobe projecting beyond the truncated surface and with 

 a subulate cirrus at its extremity, whilst the somewhat long row of caudal hooks is 

 intimately associated with its dorsal edge. No other hook or bristle is connected with it. 



The dense rows of hooks are situated on the edge of the prominent lamellae. 

 Bach has a short base or shaft (Plate CXXV, fig. 7 e) with a well-marked rounded crown, 

 a smaller and a larger fang beneath, the curve below the latter sloping to a modified 

 tooth with a 4 — 6-spinous edge, then a gulf below, and a rounded prow, the basal line 

 being slightly sinuous. 1 



The caudal appendix (scapha) presents dorsally an almost evenly truncated edge in 

 a line with the general surface (Plate CXXV, figs. 7/ and 7 g), the margin, however, being 

 minutely crenulate and projecting a little beyond the dorsal surface of the appendix. 

 Then follows the line of caudal hooks, which abut at their ventral edge on the rounded 

 and flattened lamella with the cirrus. A notch separates the ventral edge of the lamella 

 from a series of four fimbriae between it and the vent, the lower edge of which is crenate 

 with a subulate median cirrus. Nilsson 3 has recently shown the structure of the eyes of 

 this organ. The caudal hooks (Plate CXXV, fig. 7 d) are slightly narrowed at the base 

 of the striated shaft, then dilate, continue for some distance with nearly parallel sides, 

 diminish toward the neck, and end in a slight curvature at the point, which is somewhat 

 blunt, probably from friction. 



The tube is slightly curved, and in Malmgren's examples was composed of minute 

 shells, viz., Bissoa striata and Bulla truncata. Tubes from the coast of Kerry are composed 

 of comparatively large fragments of shells and stones with a minute Rlssoa. Those from 

 422 fathoms off Ireland in the " Porcupine " Expedition of 1869 were formed of proportion- 

 ally large translucent grains of quartz with here and there a yellow and black grain of other 

 material. One fragment is composed of Foraminifera with a few grains of sand, but its 



1 Malmgren figures the spinous edge as a simple process, whilst Hessle gives it six to 

 seven teeth. 



2 Beitrage Nervensyst. Polych. i Zool. Bidrag Uppsala/ Bd. i, p. 137, 1912. 



