978 MB. J. T. JOHNSOTI ON THE [NoV. 28, 



14. Tbrias senegalensis, var. bisinuata Butler. 

 One female. 



15. Belekois mesentina Cramer. 

 A pair. 



16. Glutophbissa saba, var. contracta Butler. 

 One male. 



17. Leuceeonia thaxassina Boisd. 

 One male. 



7. Note on the Habit and Mode of Growth of the Corals 

 belonging to the Genus Pleurocorallium. By James 

 Yate Johnson, C.M.Z.S. 



[Received November 2, 1899.] 



In my communication to the Zoological Society on the Coralliidce 

 of Madeira (P. Z. S. 1899, p. 57) nothing was said as to the cause 

 or meaning of the peculiar habit and mode of growth o£ the four 

 known sytecies oi Plewocontllium. Whilst the species of CoralUum, 

 such as the red coral of the Mediterranean, branch in all directions 

 and put forth then- polype-cells on all sides of the branches, the 

 Pleurocoirdlia ramify more or less in one plane and their polype- 

 cells are confined to one face of the branches. 



When Dr. Gray first alluded to the matter (P. Z. S. 1867, p. 125) 

 he said, " I have no doubt that it (the coral under description) grows 

 out horizontally from the rocks, and that they (the polype-cells) 

 arise from the upper surface of the branches." This woiUd appear 

 to have been only a conjecture ; but in his Catalogue of Lithophytes 

 or Stony Corals in the British Museum (p. 24) he went further, 

 and described them as " growing horizontally from the sides of 

 rocks," without citing any authority for the statement. The 

 facts about to be mentioned seem to throw doubt on the correct- 

 ness of Dr. Gray's view, and to suggest another conclusion. 



In describing the only known specimen of PleurocoraWmm im- 

 derense {loc. cit.), I stated that some zoophytes of rare occurrence 

 at Madeira were growing parasitically upon it. Two of these were 

 branched specimens belonging to the genera Suberea and Stenella, 

 and they were seated on different parts of their host at a distance 

 from each other. The point to which I wish to draw attention is, 

 that both these Alcyonarians had grown in the plane of the host. 

 If that had extended horizontally, they too had extended hori- 

 zontally. But can we suppose it possible that they would take in 



