Flustra. ZOOPHYTA. FLUSTRADyE. 535 



Gen. LVI. FLUSTRA. — Foliaceous or encrusting, cells con- 

 tiguous, arranged in regular series, forming mat-like ex- 

 pansions ; polypi fixed to the bottom of the cell, retractile ; 

 ovaria like pearly excrescences on the summits of the cells. 



* Foliaceous and branched, with cells on both sides of the leaves, 



139- F. Jbliacea. — Extremities rounded, cells narrow at the 



proximal, and arched at the distal, extremity, with scattered 



marginal denticles. 



Fucus telam lineam sericeamve textura sua semulans, Ray, Syn. Stirp. 42. 



— Eschara fol. Ellis, Coral. 70. t. xxix. f. 2 Flustra fol. Linn. Syst. i. 



1300 Escli. fol. Pall. El. 52.— Common on hard ground, in a few 



fathoms water. 



Height several inches, dividing irregularly, frequently palmate ; the teeth 

 on the margin of the cells are short conical processes, usually in pairs, on 

 each side at the upper angles. The substance is rigid. Body of the animal 

 is nearly twice as long as the cells, with about fourteen long slender tenta- 

 cula. 



140. Y.papyracea. — Extremities hatchet-shaped ; cells slight- 

 ly enlarged distally, margins smooth. 



Eschara pap. Ellis, Coral, t. xxxviii Sol. Ellis Zooph. 13. — T. charta- 



cea, Lamour. Cor. 104. — English coast. 



Height about two inches, irregularly divided ; of a slender delicate tex- 

 ture, like thin semitransparent paper, and of a very light straw-colour. Is 

 this species distinct from the preceding ? A specimen sent me from the coast 

 of Devon by Mr Montagu, as the species referred to by Ellis, had the cells 

 of the same shape, with similar marginal denticles as F. foliacea, and only 

 differed in being less rigid, a character not to be relied on. 



141. F. truncata. — Strap-shaped, dichotomously divided, 

 truncated at the extremities, with lengthened quadrangular 

 cells, having smooth margins. 



Fucus rnarinus scruposus albidus angustior compressus, extremitatibus 



quasi abscissis, Ray, Syn. Stirp. 43 Narrow-leaved Horn- wrack, Ellis, 



Cor. 69. t. xxviii. f. 1. — F. trun. Linn. Syst. i. 1300. — Eschara securi- 

 frons, Pall. El. 56. — Common on hard ground, in a few fathoms water. 



Height several inches ; in some cases the branches are nearly of equal 

 breadth throughout ; in others, numerous leaves arise from the sides of the 

 principal ones, which are at first narrow, but speedily reach their usual 

 breadth, rendering the coralline proliferous. It is less rigid in its growth 

 than F. foliacea, and smooth. 



** Foliaceous and branched, zoith cells confined to one side. 



142. F.carbasea. — Irregularly divided, flat, thin, cells nume- 

 rous, oblong, narrow, and truncated at the base. 



Sol. Ellis, Zooph. 14. t. cxi. f. 6, 7. Lamour. Cor. Flex. 104 — Coast of 

 Scotland, where it was first observed by Dr David Skene of Aberdeen- 

 Height several inches ; base destitute of tubular roots ; leaves narrow at 

 the base, increasing in breadth towards the slightly rounded extremity. The 

 substance is thin and transparent, with a tinge of brown ; smooth, from the 



