114 Aren icolidae 



in PI. VI, Fig. 14, is 90 mm. long; the tail is strongly contracted, 

 being only 1.1 mm. in length. In the figure the tail has been 

 represented in a rather more normal condition of extension. This 

 specimen possesses on each side a neuropodium additional to the 

 number normal for the species. The second specimen is 105 mm. 

 long, the tail being 45 mm. in length. 



The striking feature of the specimens is the small size of the 

 gills, the longest axes of which are not more than 2 mm. from their 

 origins to the tip of their terminal filaments (p. 60). The clusters of 

 filaments at the ends of the very short axes, together with the number 

 of the gills, are characteristic of the species. In the only other 

 species in which there are eleven pairs of gills, namely, A. cristata, 

 these organs are highly developed and pinnate, and are in complete 

 contrast to those of A. gladalis. 



Murdoch states that the branchial segments have six rings, but 

 the writer found in every case only five. 



The papillae on the tail are very feebly developed ; there are no 

 processes present such as occur on the tail of American examples of 

 A. cristata. 



The crotchets are similar to those of A. marina (p. 51). 



The diagram on p. 113 embodies all that could be ascertained 

 about the internal anatomy of the only fragment it was permissible 

 to use for inspection of the organs. The small septal pouches, 

 the single pair of oesophageal glands, and the nephridia, are similar 

 to those of A. marina. The statocyst is small ; its interior is shown 

 in the section figured (Fig. 39, p. 69), which indicates the origin 

 of the tube leading to the exterior. 



Types, the only specimens known, in the Smithsonian Institution, 

 Washington. 



ARENICOLA PUSILLA Quatrefages. 

 (A. claparedii Levinsen.) 



Plate VII, Fig. 15 ; Plate VIII, Fig. 18 ; Plate X, Figs. 21-25 ; 

 Plate XIII, Fig. 44 ; Plate XIV, Fig. 49. 1 



Arenicola pusilla 



Quatrefages, Hist. nat. Annel., ii, p. 266 (Coquimbo). 



Ashworth, Ann. Sci. Nat. Zool., ser. 9, x (1910), p. 115. 



Fauvel, Mem. Soc. Nation. Sci. Nat. Math. Cherbourg, xxxi (1899), p. 176. 



1 For other figures of this species, see Fig. 8, p. 41, chaetae of larva 

 Figs. 15, 24, pp, 47, 53, chaetae of adult ; Fig. 32, p. 59, gill. 



