1844.] 



317 



5. ESCHARINA* ? SAGENA. 



a, General mode of growth, the exposed surface being the reverse side of a 

 layer of cells. 



b, Cells composing portion of an inner layer ; also reverse side of the opposite 

 layer. 



c, Cells forming part of an outer layer; one of them with a gemmuliferous 

 vesicle. 



Foliaceous, cells in two or more opposite layers, successively 

 encrusting, but separable ; cells oblong or hexagonal, defined by a 

 slightly depressed line, arranged in alternate rows, but not con- 

 formably in succeeding layers; outer surface of cell nearly flat, 

 ribbed; mouth at the distal extremity, small, round; gemmuliferous 

 vesicle large, hemispherical ; accessory foraminated vesicles tioo, 

 over the mouth. 



In the notice of this coral (Synopsis, &c. p. 79., pi. xiii. f. 7.), 

 Dr. Morton describes it under the name of Flustra sagena, but 

 adds, " perhaps it is an Eschai-a." 



This polypidom differs from described species of Escharina in its 

 free, foliaceous mode of growth, in being composed of several 

 opposite, enveloping layers, and in the facility with which the 

 dorsal surfaces may be detached ; but it has been thought ad- 

 visable not to propose a new generic name for this and analogous 

 fossil corals, the characters of Escharinge being considered to be 

 not fully ascertained. The Cellepora nobilis of Esper (Pflanzen- 

 thiere, Cellep. tab. vii.) exhibits similar consecutive layers of cells, 

 but arranged around a cylindrical nucleus and not in free plates. 



The foliations are of considerable dimensions, and are variously 

 contorted (a), and sometimes anastomosed. The layers are thin, but 

 when numerous the foliations exhibit considerable thickness. 

 Specimens presenting the opposite layers in their original position 

 are not common, in consequence of the facility with which 

 they separate along the medial plane. Portions only of successive 

 layers are also to be detected, and not very frequently. The per- 

 fect outer layer was noticed in only one instance, (c) 



* Escharina Milne Edwards ; Lepralia Johnston. 



