170 IVILSON. [VOL. I. 



screw-like, the anterior end always moving ahead, but it was 

 perfectly free in any direction and quite rapid. 



Besides assisting in locomotion the proboscis also seemed to 

 serve as a steering organ, and its extreme sensitiveness ren- 

 dered it very effective in avoiding obstacles. 



The fact that this swimming took place only at night sug- 

 gests that these animals are more or less nocturnal in their 

 habits, and it may be that they can move about much more 

 freely than has been hitherto supposed. At all events this is 

 probably the mode of locomotion used at or near the breeding 

 season, and it readily explains the large numbers of specimens 

 which are thrown up on the beach after a storm at such seasons. 



This species is well known to the clam-diggers along the 

 coast and is sometimes used for bait in deep-sea fishing, but 

 not often, and is never sought designedly for that purpose. 



Determination of Species. After a careful comparison of 

 the descriptions given by Couthouy and Pourtales with that of 

 E. Pallasii by its discoverer and subsequent zoologists, and 

 with the description which follows, there seems no possible 

 doubt that those authors fell into the same error concerning 

 our American species which trapped Ouatrefages on the Euro- 

 pean form, viz., they described an Echiurns Pallasii which had 

 lost its proboscis as a new species. Accordingly Holothnria 

 chrysacanthophora Couthouy, 1838, and EcJiinrus cJirysacan- 

 thophorns Pourtales, 1851, must go to swell the long list of 

 synonyms already appended to Echiurns Pallasii Guerin-Mene- 

 ville. 



Echiurns Pallasii Gnerin-Mencville. - - Synonyms : Holothn- 

 ria chrysacanthophora Couthouy, 1838. Echiurns cJirysacan- 

 thopJiorns Pourtales, 1851. 



External Morphology. - - Body like that of all known echiu- 

 roids, spindle-shaped, tapering slightly at either end; 10-30 

 cm. 1 long (including the proboscis, 3-6 cm. long) and 3-6 

 cm. in diameter at the center (Figs, i and 2). 



1 This figure is much larger than that usually given for E. Pallasii, but is the 

 result of careful measurement and is good evidence in favor of Shipley's state- 

 ment (13). "It seems probable that E. forcipatus of Reinhardt is identical with 

 E. Pallasii, though bigger " (cf. p. 175). 



