DIPHASIA ROSACEA. 245 



in the centre of its upper surface there is always a raised 

 tubular orifice, which is surrounded by several spinous 

 projections. 



This genus has been named by Agassiz, but he has 

 given no definition of it; he merely refers to the cleft 

 border of the gonotheca as the prominent feature. He 

 has ranged under it nearly all our British species, but 

 wrongly associates with them Sertularia fusca, which is 

 referable to a very different type. 



1. D. ROSACEA, Linn. 



" LlLY OR POMEGRANATE-FLOWERING CORALLINE," EH'tS, Cor. 8, pi. iv. figS. fl, A. 



SERTULARIA KO.SACEA, Linn. Syst. 1306 ; Esper, Pflanz. Sert. tab. xx. figs. 1-3 ; 

 Lamk. An. s. Vert. ii. 119 ; Johiist. B. Z. 64, pi. xi. fig. 1 ; 468. 

 fig. 83. 



NIGELLASTRUM, Pall. Elench. 129. 



DYNAMENA ROSACEA, Lamx. Cor. flex. 175. 

 DIPHASIA ROSACEA, Agassis, iv. 355. 



Plate XLVIII. fig. 1. 



SHOOTS very slender and delicate, of a white or pale horn- 

 colour, branched, the branches alternate, distant, un- 

 equal, internodes constricted at the base ; HYDROTHEC^E 

 long and tubular, the upper portion free and more or less 

 divergent, aperture oblique, entire ; GONOTHECA (female) 

 pear-shaped, tall, shortly stalked, ivith eight longitudinal 

 ridges, terminating above in spinous processes of various 

 lengths, the outer one on each side much the longest, 

 lanceolate, incurved, with a notch on the outer edge, 

 the remainder short, crowded, and converging towards 

 the central aperture; (male) pyriform, curved towards 

 the base, traversed by longitudinal lamellated ridges, 

 which rise above into spinous points around a slender 

 tubular orifice. 



S. ROSACEA is remarkable amongst its kindred for slender- 

 ness of habit and for its delicate, papyraceous texture. It 



