112 MAHINK HI(i|,«HiY OK THE S-TPANE^i; RKII SEAi 



Note on the Genus Olathraria, Grai/. 



In 1859 Gray gave a brief description of his genus Clathrana as repre- 

 sented by C. ritbrinodis. In 1870 he referred the gemis to the family 

 Mopselladse and distinguished another species, C. acuta. 



(jrray's diagnosis of Clatliraria is as follows: — "Coral shruh-like; branches 

 cylindrical, erect, tortuous, interosculating, of nearly equal thickness ; branch- 

 lets, some free, blunt. Bark thin, granular. Cells small, immersed, nearly 

 equally scattered on all sides of the branches ; buds and branches from the 

 swollen joints ; joints elongate, wiiite. longitudinally striated ; internodes red, 

 spongy." 



Gray identified his C. ruhrinodis with Kolliker's Mopsea hicolor (' Icones 

 Histologicse,' p. 142). Kiilliker defined his genus Mopsea thus : — " Axis 

 without nutritive canals. Spicules generally as in Melithcea, but without the 

 beautiful foliaceous clubs. Length of the clubs 0'12-0"25 mm. ; length ol' 

 the larger polyp-spindles 0"18-0'34 mm." Of M. hicolor he says: — "Soft 

 joints red, hard joints white with green centre. t'ceuenchyiiia \\hite to 

 sulphur-yellow, with uneven surface. Thickness of axis 4-7 mm."' 



In the ' Challenger ' Report (1899) Wright and Studer separate Clathraria 

 from Mopsea, and give the following definition : — " Cylindrical manifoldly 

 curving branches often anastomosing, and of uniform thickness throughout. 

 The polyps are sunk in the coenenchyma. The axis includes no nutritive 

 canals. Spicules in cortex, broad and short foliaceous clubs." 



In subsequent literature we find no further mention of Clathraria, though 

 it is a very conspicuous and characteristic type. It is so unlike other 

 Melitodids that its retention as a distinct genus seems desirable. 



The specimens from the Red Sea are clearly referable to Clathraria and to 

 the species C. ruhrinodis and C. acuta. We are thus able to give the 

 habitats of these tno forms, which Gray vv'as unable to do. The note in the 

 ' Challenger ' Report that the spicules are " broad and short foliaceous clubs " 

 must have crept in by some mistake. 



The definitions which Gray gave of Clathraria and Mopsea hardly ju.stifioi! 

 him in his wide separation of the two genera, which he referred to different 

 families. He maki s no mention of the form of the spicules, and he says that 

 the branches arise in both from the soft joints. 



Kolliker's Mopsea is separated from his Melithcea by having no foliaceous 

 clubs. His definition of .\fop.iea, so far as it goes, would cover both Mopsea 

 and Clathraria. 



In the ' Challenger ' Report the genus Mopsea is re-constructed, and if the 

 definition there given be considered more satisfactory than Kolliker's, then it 

 is necessary to continue to keep Clathraria apart from Mopsea. It is noted, 

 for instance, as a characteristic of Mopsea that the branches arise mostly 

 £rom the internolos, whereas in Clathraria they arise mostly from the nodes. 



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