152 Royal Society : — 



Carpenter and Professor Kblliker as occurring in t}ie shells of 

 laollusks &c. The oi'ganisms were found in abundant fructi- 

 lication ; they are green, but otherv\dse appear to be fungi, as are 

 the parasites of shells &c. Similar parasites are to be found in 

 various coralla from widely distant parts of the world. 



Conclusions. 



Heliopora is most undoubtedly an Alcyonarian. The number 

 of its mesenteries, and the distribution with regard to them of 

 the retractor muscles, the form and number of its tentacles, are 

 decisive evidence in the matter ; and this evidence is borne out by 

 almost every item of histological structure. In the peculiar manner 

 in which the retraction of the tentacles takes place, viz. by intro- 

 version, Heliopora seems to differ from all other Alcyonarians 

 except CoraUium*. From both Coralliam and Tuhipora, Helio- 

 pora differs in that the hard tissue of its corallum shows no signs 

 of being composed of fused spicules, but in its histological structure 

 most closely resembles Zoantharian Corals. With the Milleporidse 

 and with the Pocilloporidae and Seriatoporidae Heliopora is allied 

 solely on account of its possession of tabulae. Now that an 

 Alcyonarian is added to the list of various Anthozoa possessing 

 these peculiar structures, their presence becomes of less classificatory 

 importance even than Professor Yerrill proved it to be. There can 

 hardly be a doubt that Seriatopora wUl prove to be, like Pocillopora, 

 a Zoantharian ; and Millepora is certainly very different in structure 

 from Heliopora. Heliopora thus stands quite alone amongst modern 

 forms ; and in the peculiar structure of its cellular coenenchym it 

 is so remarkable that it is unlikely that on examination of the soft 

 parts of other corals, at present known from their coralla only, 

 any near relatives of it will be discovered. Amongst extinct forms, 

 however, Heliopora has several close allies, and the genus itself 

 existed in the Cretaceous period. The genus Polytremacis differs 

 apparently only in the more perfect development of the so-called 

 septa, which reach to the centres of the tabulae. The genus 

 occurs in the Chalk, Greensand, and in Eocene formations. 

 Heliopora has, further, a very closely allied palaeozoic representative 

 in Heliolites, in which the coenenchymal tubes are provided with 

 very closely placed tabulae. 



The three genera Heliopora, Polytremacis, and Heliolites differ 

 from one another in so slight a degree that they are placed under 

 the one genus Heliopora by Quenstedt. To include these three 

 genera, a new family of Alcyonarians must be formed, for which 

 the term Helioporidae appears most suitable, which family may 

 from the recent species be thus characterized: — 



* I have found no information on this point in any of the text-books ; 

 but in Schmarda's ' Zoologie ' there is a figure of Corallium, copied from Lacaze- 

 Duthiers's 'Hist. Nat. du Corail,' in which the tentacles are drawn intnjverted 

 an thev are in Hfliopora. 



