283 



Fam. 2. IsiDiE. 



Coral branched, tree-like or fan-shaped, with anastomosing 

 branches. Axis hard, articulated, composed of alternating portions 

 of hard calcareous and flexible horny black matter. Bark granular, 

 smooth, with irregular-shaped calcareous spicula ; polypiferous cells 

 simple, more or less exserted. 



1. Isis. 



Cynosaire, Lamk. 

 Hippurium, Oken. 



Coral branched, furcate. Axis striated, branches proceeding from 

 the calcareous articulations. Bark thick, with a few interspersed, 

 very irregular and unequal spicula. Polypiferous cells scattered 

 over the whole surface, sunken. Base of coral expanded, tuberose. 



The bark is permanent and hard, but is brittle, easily removed, 

 especially if the specimens are not kept in a dry place. Lamarck, 

 who had only seen the coral without the bark, describes it as " ca- 

 duce en totalite," &c, p. 300. 



The articulations between the joints generally become obliterated 

 near the base of the coral of the older specimens, either by the con- 

 traction and solidification of the horny part, or by the horny portions 

 becoming covered with a calcareous deposit. Lamarck regarded the 

 coral in this state as a different genus, which he named Cynosaire, 

 Mem. Mus. i. 467. See Seba, hi. t. 105. n. 3. 



1. Isis hippuris. B.M. 



Isis hippuris, Linn. ; Ellis, Zooph. t. 3. f. 1, 5 (with bark) ; Seba, 

 iii. t. 205. no. 3 (old stems) ; t. 110. nos. 1 & 2 (upper branches 

 with bark) ; Esper, t. 1, 2 (upper branches), t. 3 (old stems), t. 3 a. 

 f. 1, 2 (bark). 



2. IsiDELLA. 



Coral branched, furcate. Axis smooth, cylindrical, stony, joint 

 elongate ; branches furcate, proceeding from the corneous joint. Bark 

 rather thick, with irregular opake spicula ; polypiferous cells pro- 

 duced, subcylindrical. Base of axis expanded, lobed and branched. 



1. ISIDELLA ELONGATA. B.M. 



Isis elongata, Esper, t. 6 ; Seba, iii. t. 6. f. 4. 



I. gracilis, Lamk. Pol. Flex. t. 18. f. 1. 



Mopsea mediterranea, Risso, E. Merid. 322. f. 1. 



M. elongata, Philippi, Wiegm. Arch. 1842, 38. 



M. gracilis, Dana. 



? M. erythracea, Ehrenb. 



The branches of I elongata are said to be often anastomosed, and 

 for this reason it appears to be separated from I. gracilis ; but I 

 have never seen them in that state (Lamx. Pol. Flex. 477). 



Mediterranean; Red Sea {Ehrenb.) ; ? West Indies (Lamx.). 



