228 



IMi-. II. A. Baylis on the 



8-1 nun. thick. The head (fig. 3) is similar in shape to 

 that of T. tiara, but appears to be retractile within a pro- 

 tective sheath of loose cuticle, and to be provided with special 

 retractor muscles for that purpose. The swollen basal 

 portions of the head are transversely striated, as in the type- 

 species, and the two lips {L.) are closely similar to those of 

 7. ti'at'a, each being provided with three blunt teeth, and 

 twisted sideways in such a way that the teeth of the opposite 

 lips interlock. The head measures in length (from base of 



Fig:. 4. 



Tanqua diadema. Ventral view of posterior end of a male from 

 Helicops angulatus. 



Papillae numbered as in fig. 2. 



striated portion to end of middle tooth) 0'22 mm.; the 

 maximum width of the basal portion is 0'25 mm,, and that of 

 the lips 0"18 mm. 



Four elongate cervical glands (fig. 3, C.G.) are present, 

 opening on to the basal portion of the head, as in T. tiara. 

 Tiie length of the oesophagus is only 2*2 mm. (male)-2'4 mm. 

 (female). It thus varies between about ^^ ^"^ i of the total 

 length. This is an important point of difference from the 



