1902.] NATURAL SCIE>XES OF PHILADELPHIA. 273 



the plaue of the neuropodium, but scarcely overlaps it. Its acicu- 

 lum projects farther thau the neuropodial, like which it is suddenly 

 narrowed at the end. 



The nem-opodial sette (PI. XIV, figs. 21, 22) are grouped in 

 eight rows, of which five are ventral, two dorsal and one opposite 

 to the aciculum. They are of large size, the longest doi-sal ones 

 about equaling the longest notopodials in length. Like the latter 

 they are stout. The spinous portion is relatively short, but there 

 is the usual increase in length dorsad. On a typical seta from the 

 middle of a bundle the five or six terminal pairs of spines are of 

 large size, little or not at all divided and with no lateral fringes. 

 They rapidly diminish in size and become finely ctenoid as the 

 fringes appear, and soon become continuous with the latter. Prox- 

 imally the spines become very fine and the rows crowded. On the 

 dorsahuost setoe the number of fine rows increases and the transition 

 from the coai-se to fine is much more gradual. The number of 

 spinous rows is about fourteen in the ventral, nineteen on the mid- 

 dle and thirty on the dorsal setse. On all of the neuropodial setre 

 the smooth tip is long, simple, strongly hooked and shai-p-pointed. 

 On the ventral setie it nearly equals in length the spinous region and 

 even on the dorsal ones is about one-third as long. 



The largest of the notopodial setse (PI. XIY, figs. 23 and 25) 

 are remarkable for their size and truncate ends. They are long, 

 stout, slightly curved and bear for fully one-half of their exposed 

 portions numerous close and long rows of excessively fine teeth, 

 which are frequently worn away over considerable areas. Except 

 near the tip they extend nearly around the shaft. The tip has a 

 peculiar frayed-out appearance, as though the fibres of the setre 

 had separated and spread apart. The peripheral layer is a whorl 

 of elongated scales surrounding a fibrous bundle, from the midst of 

 which a central point appears more prominently. Around the base 

 of these scales is a very dense fringed whorl. The very large setje 

 are few in number, not more than eight or ten in a bundle. 



The most usual form of the seta tip is shown in fig. 27. In such 

 the outer scales embrace the central style more closely, so that a 

 rough, blunt point is formed. Somewhat similar are the tips of 

 the strongly curved antero-dorsal setse (PI. XIV, figs. 24 and 26), 

 but these have very short scales. The slender, sharp-pointed an- 

 terior ventral setie (PI. XIV, fig. 28) approach more nearly the 

 18 



