528 Scientific Proceedings, Moyal Dublin Society. 



the uncalcified membrane between the plates of the test ; this may 

 be quite conspicuous or calcification may have gone so far that it 

 is difiicult to detect the membranous interspace (ef. PL xxv.). 



It will be remembered that in the " Porcupine " deep-sea 

 dredgings, Professor Wyville Thomson described two species of 

 Calveria (= Asihenosoma, Grrube) ; one he called C. hystrix and the 

 other C. fenestrata ; the specific name of the latter was given 

 because there were wide membranous f enestrae between the plates of 

 the corona. From the specimens before me I am compelled to 

 conclude that this is not a specific character, and that the amount of 

 calcification of the plates is a point in which individuals living 

 together may differ among themselves. Mr. Edgar Smith tells 

 me that the conchologist experiences the same variability in the 

 texture of shells. 



Thomson insisted on the large size of the orifices of what he 

 called the ovarial plates in both Calveria hystrix and C. fenestrata. 

 I observe that the size of the orifices varies within rather wide 

 limits, but I attribute this to a difference in sex. 



I have been unable to find in any specimen, and I have most 

 closely examined a large number, any of the remarkable, large 

 four- branched pedicellariae which Thomson found in C. fenestrata ; 

 and I am of opinion that the form figured by him is abnormal. 



I see no escape from the conclusion that only one species is at 

 present known from the eastern side of the Atlantic, and I venture 

 to propose that A. fenestratum be regarded as a synonym of A, 

 hystrix. 



Echinus acutus, Lamk. 



Taken from 126 fms. 20 miles N.W. off Achill Head (St. 72) ; 

 a very conical specimen ; several examples from Galway Bay. 



Echinus escnlentns, Linn. 



The variations in the form of the test of this species are very 

 remarkable. 



Echinus elegans, Diib. and Kor. 



Eight specimens from 500 fms. (St. 70) of various sizes, and 

 with a test sometimes conical, sometimes rather depressed ; 35 miles 

 off Blaeksod Bay, 250 fms. (St. 203). Another set of specimens of 



