60 



guJarly placed side by side along the stems, and are imbedded in the 

 animal matter : the spicula are so abundant as to render the coral 

 very hard. and to give it much of the appearance of a mass of arra- 

 gonite, of which it has also the form. Its stem is irregularly cylin- 

 drical, rather crooked, and slightly tapering : it throws ofiF a rather 

 thinner branch a little below the middle of the main stem ; and both 

 the main stem and its branch end in a hemispherical head, the upper 

 surface of which is covered with forty or fifty rather large coniėal 

 tubercles, each terminating in a small centrai mouth. These tuber- 

 cles are formed of spicula resembling those of the stem, the pointa 

 of which arm the apices of the cones. The centrai eones are the 

 largest and most distinct, and the marginai ones are smaller, and 

 more or less confluent. llie stem when broken exhibits similar spi- 

 cula and a few intemai cells, but it has no distinct centrai axis : the 

 conical tubercles of the head are hollow, and they doubtless inclose 

 and give exit through their centrai mouths to the Polypes which form 

 the coral. 



This coral appears to be most nearly allied to the genus Zenia (of 

 which Alcyojiium floridum of Esper is the tj'pe), and agrees with it 

 in ha^ong no distinct axis, and in having the whole surface covered 

 with large spicula, and the Polypes protruded from tubular cells at 

 the end of the branches. It dijffers, however, from that genus in 

 its spicula being much more abundant, and the coral conseąuently 

 more solid, and by no means spongy ; and in being less branched, 

 with the polype-cells forming a hemispherical head, instead of a 

 bunch of small branches. For these reasons Mr. Gray is led to con- 

 sider it as forming a new genus, vv^hich, until the animal is known, he 

 is induced to place next to Zenia, with the following characters ; 



Genus Nidalia. 



Corallium fixum, cylindricum, subramosum, subsolidum, spiculis 

 calcareis densė indutum ; apice capitato, hemisphaerico, e pa- 

 pillis conicis inseąualibus spiculiferis formato. 



Nidalia Occidentalis. Nid. corallio albido, suhramoso. 



Hab. in littore Oceani Atlantici apud Montserrat in Indiž Occi- 

 dental! . 



The specimen described is now in the collection of the British 

 Museum, 



