EXPLANATION OF THE PLATES. 



Plates I. to VIII. — CoUotypic reproductions of photographs of caUcles, 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 by Mr. A. T. Hollick to 

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



PLATE I. 

 ma. 



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



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



3. P. Cape Verde Isla7ids 3 ; „ Litho. PI. XVIL fig. 2. 



4. ., P. Cape Verde Islands 3. 

 5a. Horizontal section of P. Trinidad 1. 



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



t). Calicles of P. Belize 2 ; for growth-form, cf. Litho. PI. XVII. fig. 7. 



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



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



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



PLATE 11. 



1. Calicles of P. Barbados U ; for growth-form, cf. PI. IX. fig. 7. 



2.1 



., I Different calicles on P. Guadalupe 6. 



4. Calicles of P. Antigua 1 ; for g] 



5. ., P. Antigua .'?; 



6. P. Antigua 3 ; 



7. „ P. Antigua 4.; „ Litho. PI. XVII. fig. 4. 



8. P. Barbuda 1; 



9. „ P. Barbuda 3: 



