326 MRS. L. J. WILSMORE ON ZOANTHEiE FROM 



zooxantliellse. The parieto-basilar and longitudinal muscles are very feebly 

 developed, and the plaiting present is not well marked. In this it agrees 

 with the other Australian forms, G. Macmitrrichi and G. mutuhi, Haddon & 

 Shackleton (5). The basal canal through the greater part of its length is 

 large and oval ; distally it breaks up into 6-8 smaller canals. Proximally 

 the basal canals elongate and widen considerably, the mesoglcsa thickens and 

 the mesenteries become joined together in the centre, forming a large mass 

 pierced by the numerous basal canals and attached to the column-wall by 

 the narrow ends of the thickened mesenteries. In this way the body-cavity 

 is filled up a little distance above the base of the polyp. This mesenteric mass 

 is in direct continuity with the mesoglosa of the coenenchyme, and its basal 

 canals are in communication with lacunce in that structure. Duerden (8) 

 describes a somewhat similar arrangement in Isaurus Ducliassaingl. I have 

 not been able to trace any connection between the basal canals and the spaces 

 in the column-wall. 



Gonads. — There were no gonads present in any specimen examined. 



The distinguishing characters of G. arenacea are : — 



(1) Its markedly incrusted character. 



(2) Its weak sphincter muscle, the cavities of which are completely 



filled with muscle-cells. 

 \_G. isolata, McMurrich (4), has a few of the upper cavities of the 

 sphincter filled in the same manner.] 



(3) Its shape. It is shorter and at the same time thicker than any 



other of the smaller species of Gemmaria. It agrees with 

 G. fusca, Duerden (8), and disagrees with all others in having a 

 column of equal diameter throughout, including the capitulum. 



It is, perhaps, most closely allied to G. canariensis (Haddon & Duerden, 7) , 

 but in addition to the above general points of difference it has no cuticle, 

 a different number of mesenteries, and distinctly weaker mesenteric muscu- 

 lature, in which latter point it agrees better with the Australian species 

 G. MacmurricJd and G. mutuhi (Haddon & Skackleton, 5). 



University College, London. 

 January 1909. 



List of References. 



(1) 1886. Erdmann. Dr. — Ueber einige neue Zoantheen. (Jenaische 



Zeitschr. flir Naturwiss. vol. xix. p. 430.) 



(2) 1889. Haddon, A. C— A Revision of the British Actinise. Part I. 



(Trans. Roy. Dubl. Soc. (2) iv. p. 297.) 



(3) 1889. McMurrich, J. Playfair.— A Contribution to the Actinology of 



the Bermudas. (Proc. Acad. Nat. Sci. Philadelphia, p. 102.) 



