POLYCH^TA. — BENHAM. 187 



(2.) In all the species so far examined the elytron is fringed 

 with long filamentous processes, usually termed " cilia," over 

 the posterior, the lateral and part of the anterior margin. 



(3.) The ventral chsetae are not as figured by Thomson, 

 but are bearded, as correctly shown by Moore for his species ; 

 and a re-examination of several individuals of P. squamosus 

 shows that the short " frills," so characteristic of the Poly- 

 noids, are in reality formed by the bases of these long hairs. 

 It may be mentioned that Thomson, in his description of the 

 chsetae (p. J)81), writes : — " Rows of minute filiform spines, 

 but bearing no comb-like plates," and his figure shows short 

 hair-like processes. All the specimens at my disposal are of 

 rather large size, and these hairs have been worn away, 

 leaving short frills composed of very minute and veiy thin 

 and numerous processes, of unequal lengths. It is clear that 

 Thomson had this in view, and recognised that the chsetse 

 differed from the usual type. 



Such bearded chsetae occur also in Iphione spinosa as 

 figured by M'Intosh in the " Challenger " Report. 



(4.) It appears to be characteristic to possess on the upper 

 surface of the cirriferous segments and encroaching on the 

 feet large transversely oval cushions (the dorsal " tubercles " 

 of Grube), similar to, but smaller than, the elytrophoral 

 cushions. In the figures of Polynoids, of which the naked 

 dorsal surface is carefully drawn, these, though present, are 

 nnich less conspicuous. Their great development here seems 

 to be related to the improved respiratory system, evidently 

 serving to direct the incurrent water between the feet on its 

 May to the respiratory channel on the back, and so ensuring 

 that it passes over the gills which are set along the faces and 

 upper surfaces of the feet. 



(5.) In all the species the elytra are supported mesially by 

 a series of small " pads " along the backi — two pairs or two 

 single ones in each segment, which, as in other Polynoids, 

 are biannulate. 



The first two pads are median and belong to the first para- 

 podial segment; then follows a double series, median in 

 position and close together, which extends till the tenth, 

 thirteenth, or even, in one species, to the fifteenth segment, 

 after which comes a median series, which ceases in the nine- 

 teenth segment. The channel thus formed along each side 

 of this row of pads continues till the last elytron on the 



1. Similiar pads are shown in a few other Polynoids, e.g., Harmcthoe 

 tuheroxa, Ehlers. 



