62 



C. HEOLEY. 



Fig. 25. Young of M elaraphe 

 mauritiana, packed together 

 at high tide level on the 

 ocean reef. 



crusts of salt. Such pools, when reduced by evaporation 

 to strong brine, may yet swarm with mosquito larvae. At 

 other times the rock hollows are filled with rain water, 

 and when this happens the Melaraphe escape from them 

 to dry ground. 



When half, or a quarter grown 

 the Melaraphe mauritiana huddle 

 together (fig. 25) in companies of 

 a score or more, packed as closely 

 as possible; as adult, it is either 

 solitary or grouped by twos or 

 threes. In the lower part of the 

 Melaraphe zone appears the bar- 

 nacle, Chthamalus anbennatus 

 (fig. 26) a small white, solid, 

 elevated cone with six walls and half 

 an inch in diameter. A little lower 

 down this is joined by another bar- 

 nacle, Tetraclita purpurascens (fig. 

 27), depressed, purple, with thread 

 like radiating riblets and with four 

 plates to its shell which is about three- 

 quarters of an inch in diameter. In 

 the English Channel the barnacles 

 harbour minute Rhabdocoele worms 1 

 not yet detected here. 



The fellowship between periwinkle 

 and barnacle on the upper beach zone 

 is so intimate, that on the far-away 

 coast of Scotland, where Littorina 

 sits beside Balanus, it still persists. 2 



Fig: 26. Chthamalus 

 antennatus, enlarged, a 

 common barnacle from 

 high tide level on the 

 ocean reef. 



Fig. 27. Tetraclita pur- 

 purascens, a common 

 barnacle associated with 

 Chthamalus. 



1 Gamble, Journ. Mar. Biol. Assoc, iii, 1893. 

 p. 31. 



8 King and Eussel, Proc. Boy. Phys. Soc, 



Edin., xvii, 1909, p. 236. 



