PHARYNX OF AN UNKNOWN HOLOTHURIAN. 255 



On the Pharynx of an Unknown Holothurian of 

 the Family Dendrochirotse, in which the 

 Calcareous Skeleton is remarkably developed. 



By 



H. IV. Ifloseley, 91. A.. F.R.S., 

 Liuacre Professor of Humau and Comparative Anatomy, OsforJ. 



With Plate XXIII. 



The specimen of which an account is here given was found 

 amongst a quantity of other material dredged jn the Sulu Sea, 

 in from ten to twenty fathoms, by Captain W. Chimmo, R.N., of 

 H.M.S. "Nassau/^ 1871, and presented by him to the Ana- 

 tomical Department of the Oxford Museum. The specimen is 

 unfortunately isolated, and no traces can be found of the body 

 of the Holothurian to which it belonged. Its actual length is 

 about 1-fth inches, and because of its large size and the regularity 

 of the arrangement of the calcareous plates with which it ia 

 protected, it forms a striking object, which attracts the eye 

 of a naturalist at once. The anterior part of the pharynx itself 

 is complete, with its contained tentacles and calcareous ring, but 

 the retractor muscles are completely torn away, and posteriorly 

 no trace remains of the water vascular ring or its appendages. 

 The membrane which closed the intervals between the rows of 

 radial pharyngealia has also disappeared. The calcareous 

 plates composing the actual ring (annulus) around the anterior 

 region of the pharynx will here be termed annularia ; those 

 disposed in rows posteriorly the pharyngealia. 



The calcareous ring is composed, as is usual in Dendrochirotse, 

 of ten skeletal pieces, five radial and five interradial in position. 



