124 PROCEEDINGS OF THE ACADEMY OF [1889. 



description and figures given by Quoy and Gaimard, 1 is the slight 

 prominence of the polyps above the coenenchyme when in contraction. 

 10. Gemmaria Rusei, Duch. and Mich. (PI. VII, fig. 7-9.) 



Synon.: Gemmaria Rusei. Duchassaing and Miehelotti. 1860. 



I was pleased to find in the Bermuda collection several specimens 

 of a form which evidently belongs to the same genus as the form 

 from the Bahamas which I described as Gemmaria isolata. Several 

 anatomical features are common to the two, and I am now able to 

 give other characteristics which may serve to distinguish the genus 

 more definitely than was done in my former paper. 



The polyps of G. Rusei (PI. VII, fig. 7) are solitary, being attached 

 to pebbles without the development of any coenenchyme. The spec- 

 imens were obtained at North Rock, and are five in number. The 

 upper portion of the column is larger than the lower, so that the 

 polyps have the shape of a short stout club ; the lower portion is 

 transversely wrinkled even in the expanded condition, as is noted in 

 the label accompanying the specimens. The height of the column 

 is about 2-5 cm. in the largest specimens ; the diameter of the upper 

 part is 0-65 cm. and of the lower 05 cm. The color is stated on the 

 label to have been " cinereous throughout." 



The column wall is rather thin, and is occupied throughout nearly 

 its entire thickness by foreign bodies. The ectoderm is covered 

 externally by a cuticle, but I was unable to ascertain whether a 

 layer of mesogloea intervened between this and the surface of the 

 ectoderm. The structure of the thin layer of mesoglcea unoccupied 

 by foreign bodies is as in other zoanthidae and calls for no special 

 comment. The sphincter is single, and imbedded in the mesoglcea ; it 

 consists for the most part of a single layer of cavities, but thickens 

 somewhat towards its upper end. All the cavities contain muscle 

 cells, there being none of the empty cavities described in G. isolata. 



The tentacles are arranged in two cycles, and have only a very 

 weak ectodermal musculature, as is also the case in isolata. Towards 

 the base and upon the outer surface the mesoglcea contains peculiar 

 granular cells, and occasionally enclosures of foreign bodies, and this 

 likewise occurs in isolata. 



The disc is traversed by a number of ridges which radiate from 



the peristome to the margin, a ridge corresponding to each tentacle 



of the outer cycle. The elevations are produced by thickenings of 



the mesogloea (PI. VII, fig. 9), and along each ridge the ectodermal 



1 Quoy and Gaimar v^Zoologie du Voyage de la corvette 1' Astrolabe. Paris. 1833. 



