100 Rev. A. M. Norman on the Genera and 



have best described and perhaps figured the species. With respect 

 to the species more recently introduced into our list of Echino- 

 dermata, such references to other works are given as were thought 

 likely to be of service to the student. 



Specimens have been examined by the author from every 

 British locality which is given for the rarer species, unless the 

 name of the locality is inserted between inverted commas. 



The following is necessary to explain the measurements em- 

 ployed : — The " lesser radius " is a line drawn from the centre 

 of the disk to its edge, between two of the arms ; and the '^greater 

 radius'^ is the distance from the centre of the disk to the extremity 

 of an arm. Similarly, the "lesser diameter" is the width across 

 the disk ; and the " greater diameter '^ the measurement from 

 tip to tip of the arms. 



The second part of this paper, on the Echinoidea and Holo- 

 thuroidea, will, we hope, be illustrated by figures of the spicula 

 of the species of the last-named most difficult order. The author 

 will be much obliged to any naturalists who will send to him 

 for examination any Holothuroidea which they may think of 

 interest ; and it would be a great assistance should any reader 

 of these notes be able to inform him where the type, or, indeed, 

 any specimens are to be found of the following species — Pso- 

 linus brevis, Cucumaria fusiformis, C. fucicola^ C. Drummondii, 

 C. Montaguij C. Neillii, C. dissimilis, Thyone Portlockii, — or 

 British specimens of Holothuria intestinalis and H. tubulosa. 



It only remains to conclude these introductory remarks by 

 returning our sincere thanks to the friends who have so kindly 

 assisted us in various ways while collecting information and 

 preparing this paper. Our acknowledgments are more especially 

 due to Mr. Alder, Prof. Wyville Thompson, Mr. Jeffreys, Dr. E. 

 Percival Wright, Mr. Patterson, Mr. Hodge, Mr. T.Edward, and 

 Mr. D. Robertson. 



Glass ECHINODERMATA. 

 Order I. CKINOIDEA. 



Body pentagonal or round, more or less conical, either sessile 

 and adherent by the aboral surface or supported (sometimes, as 

 in Antedon, only in the young state, and then free in the adult) 

 on a multiarticulate, solid, calcareous peduncular column of 

 great length, the base of which is firmly cemented to foreign 

 bodies. Arms five, solid, multiarticulate, proceeding from the 

 abora' and inferior surface, dichotomously branched from near 

 the base, and frequently again and again subdivided ; ultimately 

 pinnate ; not furnished with any spines, but having numerous 

 marginal ten taenia. Aboral and inferior side of body formed by 



