Haddon and Shackleton — A Revision of the British Actiniae. 653 



Colour. — Tentacles a distinct red. 



Dimensions. — Largest polyp, 25 mm. in height, and about 5—6 mm. diameter at 

 the top when contracted. (Judging from the figure, 20 mm. is the average height, 

 and 5 mm. the capitular diameter.) 



Habitat. — Plymouth Sound. 



This species has apparently never been met with since its discovery ; and we 

 are unable to do more than recast Holdsworth's description. We have no doubt 

 that this species is an Epizoanthus ; and it very closely resembles in outward 

 appearance the specimens of E. couchii, which one of us has dredged oif S. W. 

 Ireland, the habit of growth being the most distinguishing feature, and upon this 

 we do not place any reliance. Should this species be found to be distinct from 

 E. couchii we expect that our Irish specimens would have to follow the former. 



PAEAZOANTHUS, n. g. 



Macrocnemic Zoantheae, with a diffuse endodermal sphincter muscle. The 

 body-wall is incrusted. The ectoderm is continuous. Encircling sinus as well as 

 ectodermal canals, lacunae, and cell-islets in the mesoglcea. Dioecious. Polyps 

 connected by thin coenenchyme. 



This is a very well marked genus anatomically ; but it is often impossible to 

 distinguish between certain species of this genus and those of Epizoanthus on 

 external examination only. 



We have taken for our type P. axinellce (Schmidt), as this form is so readily 

 obtainable, and, thanks to the Naples Zoological Station, is to be found in most 

 museums. Another advantage is that it is one of the easiest of the incrusted 

 Zoanthese to study microscopically. 



Erdmann was the first to separate the macrocnemic Zoantheae, Avith a diffuse 

 endodermal sphincter, from those with a mesogloeal muscle. He rightly retained 

 the genus Epizoanthus for the latter, but wrongly referred the former to Palythoa, 

 of which he also took P. axinellce as the type. We have elsewhere (1891) 

 entered into a detailed discussion of our reasons for restoring Palythoa to its type 

 species P. mammillosa (E. & S.), and we consequently have to erect the new genus 

 defined above. 



BRITISH SPECIES OP THE GENUS PARAZOANTHUS. 



P. anguicoma (Norman), 1868. 

 P. dixoni, n. sp. 



