1868.] DR. J. E. GRAY ON THE CERATELLAD^. 5/7 



slightest indication of such a covering to be observed in any of the 

 specimens I have examined ; but that is also the case in the Pontes 

 and sponges that are generally found in collections. 



The younger parts of these plant-like animals are formed of agglu- 

 tinated,' free, horny, projecting fibres, and the older parts of keratose 

 network ; so that it is probable that, as part of the animal becomes 

 old, or only required for the support of the young or more lately deve- 

 loped portion, the projecting portions become gradually transformed 

 into a horny network. 



I have not been able to discover, in the very cursory microscopic 

 examination of these specimens which the state of my eyes will allow 

 me to make, any appearance of aquiferous canals in the stem or 

 branches, such as one might expect to exist if they are sponges, or if 

 the prominences on the branches are oscules ; nor have I been able to 

 observe any indications of any lamellar star-like cavities either in the 

 prominences or cells on the branches, or in the substance of the 

 stems or branches, which ought to be there if they are madrepore 

 corals allied to Porites, even supposing that a horny coral does 

 exist ; and a horny madrepore coral would be a very aberrant form. 

 A sponge has been described under the name of Darwinella which 

 is said to be made up of horny spicules ; but I have not seen this 

 sponge, and do not know the remainder of its structure. 



I have requested Mr. M. E. Cooke to undertake to examine the 

 microscopic structure of these specimens, which the state of my eyes 

 will not allow me to attempt. He states that he has not been able 

 to discover any siliceous spicules. 



The absence of any lacunae in the structure of the stem or branches, 

 or communication with the cell for the circulation of the water, 

 which ought, according to the idea of its being a sponge, to be 

 emitted by the cell-like oscules (and the regular development of the 

 cell is much more like the budding of a fully developed polype than 

 the growth of a Protozoon or sponge), leads one to doubt its proper 

 arrangement with them. At the same time, the want of the cylin- 

 drical cells for the bodies of the actinoid polypes is equally repug- 

 nant to the idea of its being a horny madreporoid coral. 



There can be no doubt that though the two specimens of these 

 animals which I have examined are sufficiently different from each 

 other in structure and growth to be regarded as belonging to two 

 genera, yet they are so allied as to form a single family, which 1 

 propose to call Ceratellad.e. The family may be characterized 

 by the details which I have already given of their structure. 



Ceratella. 



Sponge or coral irregularly dichotomously branched, more or less 

 expanded on a plane from a single base ; of a dark brown colour, 

 of a uniform, hard, horny substance ; stem hard, dark brown, soUd ; 

 base dilated, rather compressed, of a uniform rigid somewhat spongy 

 texture, with a velvety surface, which is formed of an abundance of 

 very minute, cylindrical, tortuous grooves. Tlie branches and 

 branchlets tapering, formed of a very large quantity of nearly parallel. 



