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. moeoglcea. 



mc. mesogloeal-cells. 



me. mesenteries, 



mi. cell-islets in the mesoglrea. 



ml. lacunae in the mesogloea. 



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 Uj^sala. 



