EXPLANATION OF LETTERS. 



c. cuticula. 



d. detritus, 

 di. diatoms. 



eb. ectodermal bay. 



ek. ectoderm. 



en. entoderm. 



enc. encircling sinus. 



i. incrustations. 



if. incrustations of foraminifera. 



is. incrustations of sand. 



iss. incrustations of spicula. 



m. mesogloea. 



me. mesogloeal-cells. 



me. mesenteries, 



mi. cell-islets in the mesogloea. 



ml. lacunae in the mesoglcea. 



mu. muscles. 



n. nematocysts. 



rm. transverse muscles. 



z. zooxanthellae. 



ABBREVIATIONS IN THE TEXT. 



N. N. A. E. : Norwegian North-Atlantic Expedition. 



R. M. : Riksmuseum of Stockholm. 



U. S. F. C: United States Fish Commission. 



Ups. M., U. U. Z. M. : Zoological Museum of the university Upsala. 



