Mr. A. H. Hassall's Catuloyut of Irish Zoophytes. 371 



■which are to be distinguished from the particles of sand b}' tlieir 

 much smaller size. In a recent state a membrane is attached to 

 the edges of each cell ; this rises up in a globular form, and bears a 

 near resemblance to the papillse on A. Idrsutum. The polypi cor- 

 respond so closely with those of the other species of Alcyonidium, 

 that I have thought it superfluous to give a separate figure of it, 

 having the same number of tentacula, viz. 16. 



Encrusting various flexible corallines, Dublin Bay : common. 



A. echinatum. It is not a little remarkable, that the polypi of 

 this common species should have remained hitherto undescribed. I 

 was lately so fortunate as to meet with some specimens in which I 

 had an opportunit}- of examining the animals in a living condition. 

 The result of this examination proves, that it is not only not allied 

 to the family with which it has up to this time been classed, but 

 that it is a true Hydra zoophyte, related closely to Coryne squamata, 

 between which and Hermia ghindulosa it forms a new and distinct 

 genus. This new genus it was my wish to have dedicated to Dr. 

 Johnston, the author of the work on British Zoophytes, in acknow- 

 ledgment of the valuable services rendered by that gentleman to 

 this interesting department of natural science. In this desire I have, 

 however, been disappointed, from the circumstance of a genus in 

 botany having been dedicated to Dr. .Johnston, the editor of Girard's 

 ' Herbal.' 



The generic name which I ha^•e adopted was suggested to me by 

 my friend G. J. Allman, Esq. 



The following are the characters of the genus 



EcHiNOCHORiuM, Hassull. 



Polypidom encrusting ; surface raised into numerous rough papillae ; 

 polypi hydroid, naked, pedicellated. — A. H. H. 



Echinochorium clavigerum. Polypidom muricated with rough 

 spinous papillae about a line in height. Polypi more or less clavate, 

 not retractile ■within cells ; tentacula claviform, about ^rd the length 

 of the body, retractile. 



There are numerous indentations on the surface of the polj'pidom, 

 in each of which the base of a poh'pe is inserted ; this latter is about 

 .jth of an inch in height and is of a v.^hite colour ; its head is some- 

 what enlarged, and is surrounded ■ndth numerous contractile club- 

 shaped tentacula ; the number of these varies considerably, but fre- 

 quently amounts to between to-enty and thirty. The tentacula are 

 not arranged in any determinate order, as they always are in the 

 AscicUan t}'pe of zoophytes, but are variously disposed. This ob- 

 sen'ation applies to all Hydroid zoophj-tes. Whether the polypes 

 are separate or united at their bases, I am imable to say. See Plate 

 X. fig. 5., which is a magnified representation of this genus and 

 species. This species does, I believe, possess a stomach, which in 

 one of the polypi in the figure is seen to be everted. Fig. b, b. 



Dublin Bay and Portmarnock : common. 



A marked correspondence exists between the natural his- 

 tory of the coast of Antrim and the opposed shore of Scot- 



2 B 2 



