EXPLANATION OF THE PLATES. 



Plates I. to VIII.— CoUotypic reproduction.s of photographs of calicles, magnified five times, 

 made by Mr. T. Murray (representing Messrs. Morgan and Kidd). 



Plates IX. to XVI.— CoUotypic reproductions of growth-forms ; those with dark backgrounds 

 were taken by Mr. T. Murray from specimens in the British Museum ; those with light 

 backgrounds were taken by M. Monpillard, of Paris, from specimens in the Musee 

 d'Histoire Naturelle. 



Plate XVII. — Lithographic reproductions of drawings of specimens Ijy Mr. A. T. Hollick to 

 illustrate growth-forms alone. The approximate sizes are given in the explanations. 



PLATE I. 



FIG. 



1. Calicles of P. Cape of Good Hope 1. 



2. ,, P. Cafe, Verde Islands 1 ; for growth-form, cf. Litho. PI. XVII. fig. 1. 



3. P. Cape Verde Islands 2 ; „ Litho. PI. XVII. fig. 2. 



4. ,, P. Cape Verde Islands 3. 

 5u. Horizontal section of P. Trinidad 1. 



5h. Vertical section of P. Trinidad 1 (showing skeletal elements hollowed out by an alga), 



b. Calicles of P. Belize '2 ; for growth-form, cf. Litho. PL XXll. fig. 7. 



7. „ P. Belize 3 ; „ Litho. PI. XVII. fig. la. 



8. „ P. Barbados 2 ; for growth-form, cf PI. XV. fig. 5. 



9. „ P. Barlmdos 3 ; „ PI. IX. fig. 5. 



PLATE II. 



