TEREBELLIDAE 



183 



fang and above these a very inconspicuous row of denticles ; in the abdominal region the 

 hooks (Fig. 32 e,f) have two transverse rows of teeth above the main fang and above 

 these a number of small denticles. There is a well-marked subrostral prolongation. 

 In the hinder region the tori are gradually transformed into projecting rectangular 

 pinnules. 



This variety differs from the stem-form in having the borders of the longer type of 

 bristle apparently smooth and not striated, and the denticles of the thoracic hooks 

 are fewer and less conspicuous. 



01 MM 



OIMM 



05MM 



■OIMM 



e f 



Fig. 32. Streblosoma bairdi, var. antarctica. 



a. Bordered thoracic bristle. d. Thoracic hook seen from front. 



b. Simple thoracic bristle. e. Abdominal hook seen from side. 



c. Thoracic hook seen from side. /. Abdominal hook seen from front. 



Remarks. The differences between this variety and S. bairdi are slight, as indeed are 

 those between the latter and the tropical S. verrilli, Treadwell, of which S. crassi- 

 branchiata, Treadwell, is a synonym, and S.persica (Fauvel). There are diiferences in the 

 degree of development of the branchiae and of the eye-spots, in the position of the first 

 unciniger and in the number of denticles on the hooks, all characters subject to con- 

 siderable individual variation. I am not convinced that in S. bairdi we do not possess a 

 somewhat variable species that is cosmopolitan in distribution. S. coespitosa is dis- 

 tinguished by having sessile neuropods in the abdominal region. 



Subfamily POLYCIRRINAE 



Tentacle-bearing region of head enlarged to form a prominent, often folded and lobed 

 lip bearing very numerous tentacles. No gills. Uncini, if present, in single rows 

 throughout. 



