THELEPUS TRISERIALIS. 179 



The cephalic collar and the arrangement of the parts of the anterior end are similar 

 to those of the foregoing species, but no pigment- specks remained in the preparations 

 behind the collar, though in life they were present. A distinction, however, immediately 

 appears in the branchial region, the surface of which is more extensive, the filaments more 

 numerous and more slender. Moreover, they arise from three segments, viz. the second, 

 third and fourth. The first and largest forms a transversely elongated row of filaments 

 on segment 2, its outer edge passing ventrally considerably below the first bristle-tuft 

 behind it. The second springs from the dorsum of the third segment within {%. e. dorsal 

 to) the first bristle-tuft and is smaller, whilst the third, which is somewhat longer, arises 

 on the dorsum opposite the second bristle-tuft. The first pair is widest apart, the third 

 nearer each other. 



The body generally resembles that of the foregoing form, but is often smaller, and 

 the dorsal and ventral surfaces, glandular scutes and plates do not materially differ. The 

 bristle-tufts range from thirty to forty, the posterior region in one having about forty 

 segments devoid of them, as in T. cincinnatus. It tapers posteriorly to a slender tail, and 

 the uncinigerous processes seem to go on to the tip, thus differing from those of T. cincin- 

 natus. The anus appears to have a papillose margin. 



The first bristle-tuft arises opposite the second branchia, and as mentioned, is above 

 the level of the first branchia, and the setigerous processes are continued along the dorso- 

 lateral region to the posterior region, as in Thelepus cincinnatus, where they cease. They 

 are vertically flattened in front and throughout the greater part of their course, but 

 posteriorly they diminish to conical papillae. The anterior bristles (Plate CXXVI, fig. 9, 

 and a curved one in fig. 9 a) appear to be somewhat shorter than in T. cincinnatus, but 

 are similarly arranged in two series, a longer and a shorter. The wings in both are 

 slightly broader than in T. cincinnatus, both sets of bristles being proportionately shorter 

 and thicker. They increase in length in the middle of the body, but posteriorly diminish 

 both in size and number, especially before ceasing, yet retaining the same arrangement as 

 regards shorter and longer series. The wings in the terminal bristles are narrow. All 

 the bristles have a pale golden hue, and whilst the first few sets of bristles are directed 

 outward, the majority slope outward and backward, the terminal tufts, however, in the 

 preparations, projecting outward or even slightly forward. 



The rows of hooks commence on a fillet at the fifth segment, that is, opposite the 

 third bristle-tuft at the posterior part of the segment, and they slightly increase in length 

 to the fifteenth series, when a gradual diminution occurs ; the rows, moreover, by-and-by 

 are elevated on processes, and instead of being nearly straight they are convex forward 

 about the twenty-fourth, and this arrangement appears to be retained in the longer 

 posterior uncinigerous processes, where they occur on the anterior face of the tip. As 

 the bristles diminish and disappear the uncinigerous processes increase in prominence and 

 are ventro -lateral in position. Finally, they are minute toward the tip of the tail. The 

 hook (Plate CXXVI, fig. 9 b) is similar (generally) to that of T. cincinnatus, yet differs in 

 detail. Thus it is proportionally larger, the base longer, the stud at the anterior end of 

 the base (prow) has a different angle with the outline, is truncated at the tip, and the 

 process beneath is more prominent, though there are variations in this respect ; moreover, 

 traces of a second tooth on the crown above the main fang are common. Marenzeller's 



