92 Prof. M'Int03li's Notes /ro7n the 



contiiuied laterally to the first hranchia. This is followed 

 by another median elevation or boss with a ridge on each 

 side to the second branchia. The parts, however^ vary much 

 according to the degree of contraction or extension, the first- 

 mentioned median fold in extension becomes a boss, in front 

 of which a groove with a fillet at each side passes to the 

 mouth. Behind the second branchial ridge is a distinct and 

 longer one on each side of a median elevation, and ter- 

 minating laterally in the first bristle-papilla. The bristle- 

 tufts are directed upward and backward, commencing Avith 

 three smaller tufts, the first two of which spring from the 

 outer ends of ventral ridges connected with median eleva- 

 tions, whilst the third has only a lateral lamella. No hooks 

 occur on these anterior feet. The fourth foot presents a 

 large lamella and stronger bristles, and the five or six 

 following have also strong bristles, after which they 

 diminish to the last, which are minute — that is, not half 

 the size of the first tuft. The structure of all these tufts 

 of somewhat brittle bristles is the same, though the 

 anterior and especially the posterior show certain modifi- 

 cations. Each lias two kinds of stout bristles, viz. (1) that 

 in which the strong shaft, after widening a little above the 

 base, tapers gradually to a somewhat rigid sharp tip, and 

 (2) a shorter series in which the stout shaft tapers to the 

 commencement of the translucent terminal portion, where 

 u rudimentary double wing appears, and then it dilates into 

 a flattened spear-head tapered to a fine point. The broad 

 flattened tip is marked by fine strise directed distally. The 

 serrations are large at the base of the terminal region, 

 rapidly bcconi.e finer, then indistinct, and, finally, leave the 

 delicate hair-like tip smooth. The shafts of all are striated 

 longitudinally, and are also crossed at intervals by trans- 

 verse bars, which, however, do not affect the outline. In 

 the first tuft of bristles the two kinds are more nearly of 

 e({ual length, and in the last tuft the tips of the simple 

 forms are more gently tapered as well as often fractured ; 

 whilst the great length and tenuity of the tips of the 

 second type cause them almost to equal the length of 

 the stronger. In transverse section these bristles arc 

 rounded (not circular). 



Tiie hooks h;ivc a short horizontal shaft, a gentle curve, 

 six teeth along the front <Mlge in lat(>ral view, then a broader 

 part which, at first sight, looks like a seventh tooth, but 

 which really is a scries of more minute teeth, as in the 

 typical Pcrt'inar'ia heh/ica, then the keel below shows a 

 convexity, a hollow, and a s>mull knob at the edge. 



