M. Valenciennes on the Gorgonidse. 181 



mass^ and are protected internally by a delicate membrane, 

 which secretes a plate of corneine covered with carbonate of 

 lime. The polypes in adding to their common body secrete 

 fresh plates composed of calcareous matter and corneine, and by 

 treating these axes with an acid which removes the lime, the 

 superposed membranes are separated from each other. A^ hen 

 the internal membrane, which is often thick, as in some Plex- 

 aurcs and Eunices, only deposits corneine, the sclerobase is 

 composed entirely of homogeneous layers of this substance; 

 these have often been regarded as ligneous axes by observers who 

 recognized in their lamellar structure a certain appearance of 

 concentric layers like that of the ligneous layers of vegetables, 

 although in reality there is no resemblance between the organi- 

 zation of these sclerobases and vegetable tissues. 



These investigations have led me to revise the classification of 

 these polypes and to arrange them as follov.'s : — 



Family I. Gorgoxace^. 



Axis not effervescing with muriatic acid. 



Genus Gorgoxia. Cells opening upon a small tubercle of the 

 sclerenchyma, projecting from the stalk. 



Sp. verrucosa, V-a\.. placomus, \i\xxn., graminea, Vd\\., j^alma, 

 Pall., and 11 other species. 



Genus Plexaura. Cells opening by a simple hole pierced in 

 the sclerenchj'ma, without projections or lips. 



Sp. virgulata, Lamk., sanguinea, Lamk., rosea, Lamk., fla- 

 vicla, hamk.jflecvuosa, Lamk., homomalhi, unxnk., friabilis, 

 Lamk., vermiculata, Lamk., multicauda , Lamk., alba, 

 Lamk., laxa, Lamk., petecliizans, Pall., and 13 other 

 species. 



Genus Euxicea. Cells placed in tubular prominences of the 

 sclerenchyma, and opening under a sort of lip. 



Sp. plantaginea, Lamk., mammosa, Lamk., and 6 other 

 species. 



Genus Pterogorgia. Cells opening in series on the two sides 

 of a compressed stem. 



Sp. anceps, Ehr., and 3 other species. 



Genus Phycogorgia. Sclerobase dilated into membranous la- 

 minse like a Fucus ; sclerenchyma covered with cellular pores. 

 Sp./«<c«/'a, Yal. (Mazatlan.) 



Genus Hymenggorgia. Sclerenchyma dilated into foliaceous 

 laminae, supported on a sclerobase with simple, branched, 

 rounded, slender, separate stems. 

 Sp. quercifoliu, Val. (Guadaloupe.) 



