AMPHICTBIS GUNNERT. 73 



of one side. In a large example, again, the outer anterior are external to a line from 

 the outer posterior. 



The stomach of this form has a blind sac which opens into the ventral aspect of the 

 organ. 



Behind the sixth bristled segment the body gradually diminishes to the tail, which 

 terminates in a median anus with a lateral subulate cirrus on each side. The surface 

 is rounded and smooth dorsally, slightly flattened in front ventrally, and marked by 

 transverse glandular ridges, a distinct median groove running from the middle to the tip 

 of the tail. The length of the body varies from 1 to more than 2 inches. 



The third segment, from its greater width and prominent anterior border, indicates 

 the commencement of the bristled region. Its dorsal margin is boldly concave forward, 

 whilst its ventral edge is nearly straight, and there is little to separate it ventrally from 

 the succeeding segment. It carries on the prominent lateral region the fan-like paleae, 

 which are more or less horizontal — that is, the concavity of the fan looks upward, the 

 convexity downward, and the longest bristles are internal, their number being from 

 fourteen to twenty. They are flattened golden bristles minutely striated longitudinally 

 (Plate CXXIV, fig. 5), the striae ending in granules distally, whilst the finely tapered tip 

 is translucent. A few transverse bars occur here and there on the shaft, which dilates 

 from the base to the surface of the skin, and then gradually tapers to the attenuate tip. 

 They form two groups, an anterior longer and a posterior shorter, the former probably 

 representing the dorsal division, the latter the ventral. 



The anterior region has seventeen pairs of dorsal bristles, the first two of which are 

 small, but the rest are conspicuous tufts projecting from setigerous processes which, 

 when viewed from above downward, are nearly cylindrical, but antero-posteriorly are 

 slightly tapered distally, and have at the ventral edge of the bristle-tuft a clavate papilla 

 which seems to have escaped Malmgren. This clavate papilla is less developed in front 

 than in the posterior setigerous processes, where it is much larger distally. The bristles 

 (Plate CXXIV, figs. 5 a, 5 a and 6 a") have straight striated shafts which dilate a little 

 from the base upward, continue of nearly equal diameter to the commencement of the 

 wings, and then curve slightly backward and taper to a fine tip. The striae of the shaft 

 become oblique in the curved terminal region, and the wings themselves are striated for 

 some distance upward. These bristles are evidently much used by the annelid, and the 

 basal striated portion of the wings is often worn. A transverse ridge with a small dorsal 

 cirrus — curved downward — represents the dorsal division behind the foregoing, and 

 continues to the tip of the tail. 



The hatchet-shaped lamellae for the hooks commence on the ventral surface of the 

 seventh segment at some distance from the setigerous process and at the posterior edge 

 of the segment. A more or less distinct ridge, wider anteriorly and gradually diminishing 

 posteriorly, connects them with the setigerous processes. The first are small and little 

 elevated, but they increase in prominence, and gradually approach the setigerous process, 

 so that at the twelfth or thirteenth bristle-bundle they are close to it; and the tip of the 

 last is nearly as prominent. Thereafter the uncinigerous processes form conspicuous 

 lamellae on each side of the posterior region to the tail. The uncinigerous lamella has in 

 the preparations a slightly irregular or crenulated edge to which the hooks are attached, 



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