E. MARSHALLI. YOUNG SPECIMENS. 103 



the lateral wall are present in about the same numerical propor- 

 tion. Both the dermalia and the gastralia are almost exactly 

 like those of the lateral wall. 



The bottom-plate is spiculated in essentially the same manner 

 as the lateral wall, except that here the parenchymalia, which 

 are again mostly thetactins with slender rays, run almost always 

 singly and in various directions, combining but seldom into loose 

 fascicles. The plate is therefore weakly supported and easily 

 breaks down. The dermalia and the gastralia differ in no way 

 from those of the lateral wall. The former are irregularly arranged 

 instead of forming a regularly meshed latticework. 



Young Specimens. 



I have before called attention to points by which the early 

 postembryonal stages of E. imperialis and E. marshalli, though 

 closely alike in general outward appearance, may be distinguished 

 (p. 79). Now, from Dôketsba I have not a small number of 

 young Eupledella in various stages of growth, all of which I do 

 not hesitate to refer to the present species. Apart from the 

 circumstances that no other species of Euplectella is known to 

 occur in that locality and tliat the specimens in question form 

 an uninterrupted series leading up to such as have the charac- 

 teristics of E. marshalli fully and unmistakably developed, I have 

 sought to establish the correctness of my identification by ascer- 

 taining the size of the floricome in each specimen. This, in all cases 

 with which we are now concerned, has been found not to exceed 

 80 /^ in diameter, exactly as it should not if the specimens were E. 

 marshalli ; whereas, in all those young specimens of similar size, 

 which I have referred to E. imperialis, the diameter reached 91 fx. 



