364 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



and other details, agreed for the most part in having the 

 head more rounded in outline than is the case in Tet- 

 rastemma melanocephalum and in this respect differed 

 slightly from the deeper water form described below. In 

 colour the majority were of various shades of yellow — 

 from pale straw to deep apricot-yellow — flesh-coloured, 

 yellowish brown and dull orange varieties were also 

 observed while a few were of a greenish-yellow, the pre- 

 vailing yellow tint being modified by the green colour of 

 the alimentary tract, but no specimen was met with at 

 all resembling the bright green type figured by M'Intosh. 



No example of this shore form exhibited any trace of 

 opaque white either on the head or in the form of a 

 median dorsal line. Only two individuals were found 

 showing a tendency by the development of brown pigment 

 on the head to connect this species with the two following 

 ones. Both were mature females agreeing in other 

 respects with the more typical specimens of T. candidum 

 from the same source. In one, about 1 cm. long, there 

 was a band of brown pigment between the anterior and 

 posterior eyes on each side but not quite reaching the 

 latter ; in the other an obscure brown patch extended 

 across the head immediately behind the anterior pair of 

 eyes, the colour being more pronounced between the 

 anterior and posterior eyes on each side. 



In the deeper water (15 to 20 fathoms) outside Port Erin 

 on shell and coralline bottom, a rather well marked form 

 was found, which may be described here since it lacks 

 the characteristic markings of the two following species. 

 It is, however, quite a debateable point whether it ought 

 not rather to be added to the series formed by Hubrecht's 

 species T. melanocephalum, T. coronatum and T. diadema 

 as an extreme variety of T. melanocephalum. It seems 

 to come very close to T. diadema but in none of the many 



