CH^TOGNATHA OB^ THE SCOTTISH NATIONAL ANTAECTIC EXPEDITION. 983 



large, very much longer in proportion than that of S. hexaptera, and almost touching 

 the posterior fin ; the anterior teeth are small, somewhat conical in shape, and overlap 

 one another, quite unlike the long divergent teeth of S. hexaptera ; the teeth are few 

 in number in young forms and more numerous in older ones, the reverse being true with 

 S. hexaptera ; the anus is situated well in front of the tail septum. In the Scotia 

 specimens the position of the seminal vesicles is a little different from that described 

 by Ritter-Zahony ; they hardly extend as far forward as the posterior fin, and the tail 

 fin is only slightly removed from them. 



Some of the specimens in this collection are noteworthy on account of their very 

 large size ; indeed, one of them seems to be the largest "Arrow Worm" that has been 

 taken up to the present time. Five specimens were over 70 ram. in length, the largest 

 of all being no less than 90 mm. long. Some measurement of this relatively enormous 

 animal may help to give an idea of its size. The length exclusive of the tail fin is 

 88 mm., the tail fin being at least 2 mm. long, but as it is damaged rather badly it was 

 very probably somewhat longer than this. In any case the total length of the animal 

 is certainly not less than 90 mm. The tail portion, exclusive of the fin, is 11 mm. 

 The size of the head is of little importance, as this varies so much according to the 

 state of contraction, but it may be mentioned that in this specimen the head is 4 mm. 

 long and 6 mm. broad. The broadest part of the body is 8 mm. in width, and this 

 point is in the region of the ventral ganglion, 22 mm. from the tip of the head. From 

 this point the body tapers gradually towards the tail and somewhat more abruptly 

 towards the head, the body being .'} mm. in width at the tail septum and 4 '5 mm. at 



Length. 



Tail- 



Jaws. 



Ant. Teeth. 



Post. Teeth. 





percentage. 









88 



12-5 



5 



5 



? 



80 



12-5 



6 



7 



9 



79 



12-6 



6 



5 



? 



78 



12'9 



5 



7 



9 



72 



12-5 



6 



7 



5 + 



65 



11-5 



6 



9 



10 



60 



14 



5 



8 



9 



59 



13 



5-f- 



54- 



1 



58 



1 15-5 



7 



7 



11 



51 



13 



8 



5 



9 



50 



14 



8 



8 



9 



47 



12-8 



7 



7 



9 



42 



13 



7 



4 



8 



40 



12 



10 



6 



9. 



33 



15 



7 



4 



5 



the neck. The anterior fin commences 5 mm. behind the posterior end of the ventral 

 cranglion — the ganglion itself is 2 mm. long — and extends backwards for about 29 mm. ; 

 there is a space of about 5 mm. between the anterior and the posterior fins ; the 

 posterior fin is about 17 mm, long, and lies almost entirely on the trunk portion of the 



