f5 Prof. M'lutosh's AiUe^ from the 



characteristic lanceolate enlargement, from -svliicli the taper- 

 ing: tips slope slightly inward. Tlicse dilfer from the 

 anterior groups in being all of one length, and appear to 

 be ranged round a central papilla. The tips are com- 

 paratively short, with somewhat broad wings, which are 

 oijliquely striated and serrated along the wide or lower 

 edge. The setigerous processes and bristle-tufts remain of 

 the foregoing structure till near the posterior end, where 

 longer and finer bristles project from the small processes. 

 In these modified processes the bristles are fewer and of two 

 kinds — viz., a long slender series without a visible wing, 

 which have long, gently tapered, and slightly curved tips; 

 and, secondly, a shorter series with rather longer tips than 

 those in front and with striated wings. 



The anterior iiooks are typical avicnlarian forms with a 

 marked forward curvature of the crown and a single acute 

 main fang, the free edge of which is minutely serrated 

 tliroughout the greater part of its extent, leaving little 

 more than a third smooth, and the tip is often slightly 

 turned up. The anterior outline has a wide gulf under the 

 fang and a boldly rounded prow, whilst the j)osterior outline 

 is convex, and the base is consideiably p'rolonged in this 

 direction and abruptly finished. Curved strite occur at the 

 throat, longitudinal strise on the body, and horizontal striae 

 in the base of the hook. The hooks form a single row. 

 Accompanying each hook in this region is a paddle-shaped 

 bristle, the wings and tip of which are membranous and 

 translucent. The huoks in the middle and posterior regions 

 likewise form a single row, and have very much the same 

 structure as those above-mentioned, except that the pro- 

 longation of the base posteriorly is less, and no paddle- 

 shaped bristles occur. The posterior hooks, moreover, are 

 considerably less. 



In a small specimen, j*j of an inch long, only three rows 

 of ventral hooks were present, so that the number increases 

 with age. Six brown pigment-specks occur behind the 

 branchicP, The tube of this example is leathery and 

 brownish, with minute mud-particles on its surface and 

 clear granules here and there. Another young form was in 

 a tube projecting from a mass of Alojunidtuin parasiticui/i 

 growing on Serlularia ruyosa and Ascidians tossed on shore 

 at St. Andrews. 



A young example procured on the West Sands, after an 

 October storm, measured after preservation -^q of an inch, 

 and it had about 60 segments. The first two bristle-tufts 

 are somewhat short, the third to the sixth are long, and 



