260 H. N. MOSELEY. 



the pharyngeal skeleton of small forms with that exhibited by 

 the present relatively giant form, in cases in which they are not, 

 as in Semper's magnificent work, figured with especial care, but 

 it appears that the radial pharyngealia are in Stereoderma 

 Murray! (Jeffrey Bell)^ in direct lateral opposition with one 

 another, as in the present specimen ; but here, too, the annularia 

 appear scarcely differentiated. I am much indebted to my 

 friend. Professor Jeffrey Bell, to whom I showed my specimen, 

 for pointing out to me the resemblance to it of the pharynx of 

 this new form of his, and much other valuable information* 

 The spicules in the tentacles of the present form (see plate, 

 fig. 3) are not unlike those of some species of Thyone. Pro- 

 fessor Bell informs me that he will shortly publish an account 

 of a new Thyone, in which the pharynx nearly resembles the 

 present one, excepting of course in size. Thyonidium 

 japonicum of Marenzeller^ is another allied form which has 

 well-developed pharyngealia. 



The principal interest of the specimen above described lies, 

 as I before stated, in its large size, and more especially arises 

 from its possible palseontological significance. Had a cylin- 

 drical or cup- shaped structure of the size of the present pharynx 

 been found in the fossil condition, similarly composed of sym- 

 metrical rows of calcareous plates, it would hardly have been 

 recognised — at all events, had the annularia been imperfect — 

 as Holothurian; and it is just possible that the publication of 

 the present account and figure may lead to the recognition of 

 fossil Holothurian remains hitherto undetected. 



The radial annularia of Holothurians being now generally 

 admitted to be homologous with the auriculse of Echinoids, the 

 series of pharyngealia must, had they any homologues in that 

 group, be represented by plates on the pharynx, between the 

 superior extremities of the auriculse and the water vascular 

 ring; but none such occur, and the series of plates, highly 

 differentiated and regular as they are, appear to be without 

 homologues in other groups of the Echinodermata at all^ except 



1 Jeffrey Bell, ' Proc. Zoo). Soc.,' 1S83, PI. xv, fi^. 60. 



2 Marenzeller, ' Verli. zool. botan. Ges. Wien,' 1881, 1882, Taf. v, 9. 



