158 PROCEEDINGS OF THE ACADEMY OF [Jan., 



double-ranked, veiy close together, and have a nearly uniform length 

 of 1.3 mm. to the end of the radioles. No eyes are visible. The second 

 radiole from the dorsum of the right side terminates in a membranous 

 vesicle which is probably pathological, but which would act much like 

 the operculum of Apomatus. The branchial lobes are slightly involute 

 ventrally. The collar is stiff and erect, separated by the entire width 

 of the body dorsally, but prolonged ventrally as a pair of abrupt promi- 

 nent narrow lobes in contact at the base. Except for very slight 

 lateral emarginations the margin is entire. The thoracic region is 

 nearly terete, the abdominal somewhat depressed and of a uniform 

 width except at the tapering caudal end. There are 8 setigerous 

 thoracic and 55 or 56 abdominal somites, mostly distinctly marked 

 and uniannulate. Thick and very distinct ventral plates occupy the 

 neural third of the boch^ Those of the thorax are tmce as wide as 

 long and undivided, except the first, or peristomial one, which is as wide 

 as long and of a sugar-loaf shaped outline. The first abdominal ])late 

 is pentagonal, the others are divided into two equal squares by the 

 fffical groove which is very distinct ventrally, but, after turning to the 

 right in the fiu'row '^/ x, and bending forward on IX, disappears totally 

 on the side of the latter below the setse. There is no trace of the dorsal 

 groove. The setigerous and uncinigerous tori are strictlj' lateral and 

 not elevated above the general surface of the body; the latter diminish 

 in size caudally. The body cavity is filled with rather large eggs. 



All of the setse (PI. XI, fig. 1) are of the winged capillary type, but 

 differ considerably in length, slenderness and width of the wing. They 

 are very nearly straight, ver}^ acute, and, although obliquely striated, the 

 wings have entire margins. Both avicular and pick-shaped micini 

 occur on the thoracic, the former only on abdominal somites. Their 

 number is alwa5^s small — e.g., 27 of each on III, 21 on VI, and 20 on 

 Vm, while never more than 18 of the avieukie only occur on abdominal 

 somites. In both regions they rapidly diminish in size from the end 

 of the tori nearest to the setae, the smallest in the abdominal tori 

 not exceeding ^ the size of the largest. In the thoracic region the 

 same statement applies to the pick-shaped hooks. The thoracic 

 avicular uncini (fig. 39) have elongated bodies, about eciualling the 

 elevated neck and head, the posterior process slender and produced, 

 and the breast small, but abrupt and strongly convex. The neck 

 meets the body nearty at a right angle, is high and erect, and curves 

 broadly and regularly into the stout tapering beak \\dthout any dis- 

 tinct enlargement into head or crest. The crest is represented by a 

 fine striation near the vertex without anv elevation or free teeth. The 



