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On Anthura gracilis (Montagu). 

 By 



E. W. Sexton. 



With 12 Figures in the Text. 



On August 14th, 1913, a fine male specimen of Anthura gracilis was 

 taken by the Oithona, in the young-fish trawl working at the surface at 

 night, about six miles west of the Eddystone. 



An excellent account of the female and young male has been given 

 by Norman and Stebbing {Trans. Zool. Soc, Vol. XII, p. 122), but, 

 as far as I am aware, the adult male has never been described, and as 

 it differs considerably in appearance from the female, I have figured it 

 here, adding to Norman and Stebbing's description some notes made 

 on the Plymouth specimens. 



Female specimens are occasionally found in the dredgings from Ply- 

 mouth Sound, but males are rarely captured. 



Very little is known of the habits of the species. The females are 

 evidently much more sedentary than the males ; they are more heavily 

 built, the body stouter, the mouth organs larger, and the first gnatho- 

 pods much heavier and bigger than in the male (cf. Figs. 9 and 11). 

 Stebbing, in his History of Crustacea, 1893, p. 335, makes an interesting 

 suggestion with regard to these animals and their mode of life. In 

 referring to the Eisothistos veryniformis of Haswell and its habit of living 

 in the tube of a Serpula with its tail at the mouth of the tube, the uropods 

 and telson mimicking in appearance the operculum and branchiae of 

 the worm, he says : " Probably the British Anthura gracilis may use a 

 similar shelter, since it is undoubtedly dredged up in company with 

 shells and stones on which the tubes of Serpulse are abundant." An 

 observation recently made by Mr. Crawshay {Mar. Biol. Journ., Vol. IX, 

 No. 3, 1912, p. 351) appears to support this suggestion, at least as far 

 as the female is concerned. In the material trawled at forty-two fathoms 

 he found one specimen of this species, a female, head inwards in a tube 

 of Sahellaria spinulosa. He noted the position of the tail appendages 

 lying nearly flush with the opening of the tube, and added : " Their 



