246 DISCOVERY REPORTS 



ribbing on the inner surface. As has already been stated, two introverts were found in 

 the collection, one of which was included in the same tube as a specimen of E. antarcticus 

 and the other was in a tube alone. Spengel (1912, p. 200) also found a similar unattached 

 introvert which he assumed belonged to this species. The two introverts in the Dis- 

 covery collections were very similar. The one from St. 167 measured about 65 mm. in 

 length and about 18 mm. at its broadest part. At the posterior end where it had been 

 attached to the body it was rolled into a small tube for a distance of about 5 mm., 

 thereafter broadening out into a more or less uniform wide flap. At the anterior end it 

 was slightly T-shaped. The colour throughout was cream, except along the edges where 

 it was light brown. The inner surface was practically smooth throughout, except for 

 a slight ribbing along the edges. The introvert found at St. 190 was in all respects 

 similar. It was about 50 mm. in length and about 1 1 mm. at its greatest breadth. 



The third distinction lies in the number of nephridia. In E. echiurus there are two 

 pairs and in E. antarcticus Spengel suggests that there may be three pairs. The nephridia 

 are evidently easily destroyed and seem to macerate first, and in most cases I was unable 

 to come to a definite decision as to the number of nephridia in the Discovery specimens 

 except in the case of three of the specimens where there seemed definitely to be only 

 two pairs. 



Thus, of the three suggested distinctions between the two species given by Spengel 

 only the difference in the shape and structure of the introvert seems to be valid, 

 judging by the Discovery specimens. Spengel had doubts as to whether the two species 

 were really distinct. They are without any doubt very closely related, but the very 

 different structure of the introvert would seem to suggest that in the meantime the 

 two should be kept apart. 



In most of the specimens the setae in the two posterior rows were too damaged to 

 make it possible to count them, but fortunately in several of the specimens the rows 

 appeared to be complete, and the counts were as follows: In the five specimens from 

 Larsen Harbour two had seven setae in each row, while the remaining three had seven 

 setae in the inner row and eight in the outer row. In the animals from West Cumberland 

 Bay there were nine setae in the inner row but the outer row was too damaged for 

 counting. In the specimen from East Cumberland Bay there were eight setae in each 

 row. Taking the collection as a whole, there would seem to be, on the average, seven to 

 nine setae in the inner row and seven to eight in the outer row. There would seem to 

 be a good deal of variation, since Spengel (1912, p. 201) gives for his specimens ten 

 setae as the number in the outer row and five in the inner row. 



Genus Urechis Seitz 



2. Urechis chilensis (Miiller). 



Echiurus chilensis Miiller, 1852, p. 21. 

 E.farcimen Baird, 1873, p. 97. 

 E. chilensis Miiller, Fischer, 1896, p. 6. 

 Urechis chilensis (Miiller), Seitz, 1907, p. 323. 



