LEPRALIA FOLIACEA. 301 



FOLIACIA, Lank. An. B. Vert. ed. 2, ii. 266 : Milne-Edw. Ann. d. 

 So. Nat. vi. 36, pi. iii. fig. 1 : Couch, Corn. Faun, pt iii. 

 131 : Johnst. B. Z. ed. 2, 350, pi. Ixvii. : Busk, B.M. Cat. 

 ii. 89, pi. cri. flgs. 4-7; Heller, Bryoz. d. Adriat. Meer.38 : 

 Manzoni, Bryoz. foss. ItaL, Contr. iv. 18, pi. i. fig. 4, and 

 pi. iv. fig. 24, &c. 



Zoarium foliaceous, membrane-calcareous, rising from a 

 spreading crust, composed of thin expanded plates, 

 sinuous and variously contorted, with an entire margin, 

 which frequently anastomose and form cavities of 

 different shapes and sizes ; when living, of a delicate 

 flesh-colour. Zocecia disposed in two layers placed back 

 to back, or occasionally in one layer only, ovate-elon- 

 gate, or rhomboid, quincuncially arranged, separated by 

 lines, very moderately convex ; surface punctured and 

 often nodulous, the punctures frequently surrounded by 

 thick reticulated ridges, sometimes areolated round the 

 margin ; orifice arched above, contracted a little below 

 the middle, where there is a small denticle on each side, 

 the lower margin almost straight, or very slightly ele- 

 vated in the centre ; immediately below it a prominent 

 central avicularium, with a rounded mandible pointing 

 downwards, sometimes replaced by a spatulate avicula- 

 rium. Ooecia large, often subimmersed, a little flat- 

 tened in front, smooth and shining ; in fertile cells the 

 peristome is raised at the sides, and carried up on the 

 front of the ovicell. 



Colonies forming large foliated and chambered masses, 

 of very brittle texture and of a brownish colour, when 

 dead. 



Var. a (/ascialis). Divided into narrow, ligulate seg- 

 ments, frequently anastomosing. 



Var. /9 (bidentata, M. -Ed wards). A pointed projection 

 encroaching on the orifice at each side, and giving it a 

 trifoliate appearance (Plate XLVII. fig. 4). 



RANGE OF VARIATION. In the young cells the walls are 



