POLYZOAN CORALS 163 



There are no horny nodes in Hornera, and consequently 

 the coraUum is perfectly rigid. 



The two species of this genus which occur in the British 

 area are seldom more than an inch in height and occur in 

 deep water (20-200 fathoms) attached to other corals and 

 foreign objects. 



The particular interest of the genus is that it is one of 

 the many corals that were referred by Linnaeus and the 

 earlier writers to the genus Millepora, and was called by 

 him the Lichen millepore on account of its resemblance 

 to his Lichen fruticulosus seu foliaccus. The genus Mille- 

 pora is much more restricted now than it was in the time 

 of Linnaeus, when it served as a receptacle for any kind 

 of coral whose affinities could not be more accurately deter- 

 mined. No naturalist of modern times would refer Hornera 

 to the Milleporina, but there is a certain resemblance to 

 be seen between some forms of Hornera and the Stylasterine 

 genus Errina (see p. 154), and there can be little doubt, 

 judging from the excellent drawings which illustrate their 

 memoir, that the species described by Jullien and Calvet ^ 

 as Hornera verrucosa is really a species of the genus Errina. 



Heteropora. — The genus Heteropora has been the 

 subject of a good deal of controversy and has been mistaken 

 for a Millepora. It has now been definitely identified as a 

 Polyzoon, and its affinities are probably with the Cyclo- 

 stomata rather than with the Cheilostomata. 



It consists of a broad attached base from which a number 

 of short dichotomously branched stems arise which end 

 bluntly. A large specimen may be 4 or 5 inches in diameter 

 and the branches 10-20 mm. in height by 5-6 mm. in dia- 

 meter. The substance is hard and calcareous, and the 

 surface is perforated by numerous small pores of various 

 sizes. These pores are clearly not of two categories, large 

 and small as in Millepora, but vary from a minimum 

 diameter of 05 mm. to a maximum of -3 mm.- When seen 

 in vertical section these pores are found to pass down into 



1 Catnpagnes scientifiques du Prince de Monaco, fasc. xxiii., 1903. 

 - These measurements are taken from a specimen of H. pelliciilata 

 from New Zealand. 



