HOLOTHURIANS. 



183 



sioiis. //. inarmoratu, from the East Indian islands, Fijis, etc., reaches a foot in 

 length, and II. teiiuissima attains a li'nuth of two feet, and a thickness of six or seven 

 inclies. 



In some species of Ilolothuria, as in //. maniwrata, the ambuhicral jjrocesses of the 

 lower snrface only are truly ambuhicral feet, the others are papilla; : in another group, 

 including- H. ttnuissima, the suckers or papilliB are all alike, and in still another the 

 ambulacral feet upon the ventral surface are mucli closer together than those upon the 

 back. 



Ilolothtiria Jtufidana is abundant on the Florida reefs just below low-water mark, 

 and reaches a length of fifteen inches. The calcai'eous pharynx leads to an alimentary 

 canal which is about three times the length of the body, and ends in a large cloaca. 

 The branch of the respiratory tree which is attaclied to the body-walls extends to the 



. Ibl. — tjiidoihii-fi/la 



]iliarynx. The Polian vesicles are numerous, the largest an inch in length, and the 

 Huidreporic body has upon it a group of about thirty stalked processes, the largest 

 about a quarter of an inch in length. The tentacular amjjullte are twenty in number, 

 long and slender. 



Order IV. — DIPLOSTOMIDEA. 

 This order, or sub-class, established by Semper to contain the singular I!/tojiiili)duta 

 lu(jenifonnls, is characterized by a nearly spherical body, with the mouth and anus 

 close together, and ten ambulacra. Semper regards it as the type of a fifth class of 

 echinoderras. 



RhoiKtlodina laijettlforinU has a fiask-shaped body, and the mouth and anus are at 

 the narrow end of the tiask, the former surrounded by ten tentacles, the latter by ten 

 papilla; and by as many calcareous plates. A ring of ten calcareous plates surrounds 



