202 



THE ANATOMY OF INVERTEBKATED ANIMALS. 



Superiorly, the notopodium carries two transverse rows of 

 more slender organs of a similar nature, the setce : the proxi- 

 mal set are much shorter than the distal, but even the latter 

 do not attain, a length of more than T ^ of an inch (Fig. 52, 

 Q). 



The proximal set are somewhat knife-like in shape if viewed 

 in profile, consisting of a comparatively short, straight " han- 

 dle," by which they are imbedded in their sacs, and of a thick, 

 rounded, curved,blade, tapering to a fine point at its extrem- 

 ity. Close-set transverse ridges, finely serrated at their edges, 

 and inclined obliquely to the surface of the blade, traverse 

 its convex anterior circumference, leaving the back free. The 

 distal setae (Fig. 52, G) have a very similar structure, but they 

 are much elongated and very slender. The handle is longer ; 

 and the blade, little curved and simply set on an angle with 



PIG. 52. Polynoe squamata. 



A, elytron viewed from above. B, a tooth. ^ <?, Z>, nenropodial setae. E^ F, parts of 



the blade of the same, more highly magnified. G, free extremity of a notopodial 



seta. 



the handle, is produced at the end into a long and delicate 

 filament. The base of the blade (E) is beset with incomplete 



