POLYNflE SQUAMATA. 



single median one. The latter (a), or the prcestomial tentacle 

 ("untenne mecliane," Milne-Edwards), is aim il;u in stru 

 to an ordinary cirrus. Of the other appendages, the upper 

 one upon each side (supero-lateral praestomial cirrus, " an- 

 tenne mitoyenne ") also resembles an ordinary cirrus (b) ; hut 

 the lower (infero-lateral pmestomial cirrus, " antenne ex- 

 terne ") (b 1 ) is much larger, and is capable of extreme elon- 



Pio. SS.Polyndesquamata. 



A. Posterior extremity from above : <?, notopodial cirras of last eomite; d, pygidlal 

 cirri ; #, anue. 



B. Anterior extremity from above : a, pnegtomial tentacle ; 6, superior and V 

 inferior pnestomial cirrus ; <: <?, notopodial and netiropodial cirri ; t \ peduncle 

 of flret elytron ; /, praestomium ; m, parapodium of pcristomium. C. Inferior 

 view of auterior extremity, letters as before. 



gation and contraction, 1 while the ordinary cirri are merely 

 flexible. Although at first sight probable, yet it would ap- 

 pear, from Max Mtlller's account of the development of Poly- 

 noe 9 that these two appendages do not, like the two peristo- 

 mial cirri which they essentially resemble, correspond with 

 the notopodial and neuropodial cirri of a single parapodium, 

 inasmuch as they arise from perfectly distinct portions of the 

 praestomium. It is very possible that each represents the 

 appendage of a somite, and in this case the prartomhun 

 would be composed of at least two somites. Whether the 

 praestomial tentacle indicates another, or whether it is merely 



1 1 have never observed any invagination such as is stated to oooor by 

 Audouin and Milne-Edwards, 1834. (" Histoire NatureUe du Littoral de La 

 France," p. 10.) 



