72 MARINE BIOLOGY OF THE SUDANESE RED SEA. 
Note on the Genus Clathraria, Gray. 
In 1859 Gray gave a brief description of his genus Clathraria as repre- 
sented by C. rubrinodis. In 1870 he referred the genus to the family 
Mopselladee and distinguished another species, C. acuta. 
Gray’s diagnosis of Clathraria is as follows:—“ Coral shrub-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, white, longitudinally striated ; internodes red, 
spongy.” 
Gray identified his C. rubrinodis with Koélliker’s Mopsea bicolor (‘ Icones 
Histologice,’ p. 142). Kdlliker defined his genus MJopsea thus :—‘“ Axis 
without nutritive canals. Spicules generally as in Melithva, but without the 
beautiful foliaceous clubs. Length of the clubs 0:12-0:25 mm. ; length of 
the larger polyp-spindles 0:18-0:34 mm.” Of JM. bicolor he says :—“ Soft 
joints red, hard joints white with green centre. Coenenchyma white to 
sulphur-yellow, with uneven surface. Thickness of axis 4-7 mm.” 
In the ‘ Challenger’ Report (1899) Wright and Studer separate Clathraria 
from Jlopsea, and give the following definition :—‘t 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. rubrinodis and C. acuta. We are thus able to give the 
habitats of these two forms, which Gray was 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 justified 
him in his wide separation of the two genera, which he referred to different 
families. He makes no mention of the form of ihe spicules, and he says that 
the branches arise in both from the soft joints. 
Kolliker’s Mopsea is separated from his Melithwa by having no foliaceous 
clubs. His definition of Mopsea, 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 
from the internodes, whereas in Clathraria they arise mostly from the nodes. 
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