80 ECHINODERMATA. 



It also exhibits a considerable difference both in the form and in 

 the general distribution of the parts from the rest, which, were there 

 others to follow, would sanction its position at the head of one subdivi- 

 sion of the tribe. But, in the present state of knowledge, such a mea- 

 sure, as before observed, would only resolve into the distribution of 

 species, not the institution of genera. 



The peculiarity of aspect here partly ensues from the diiferent 

 arrangement of the parts. The suckers of the Holothurise are usually 

 dispersed throughout the total extent of the body, either promiscuously 

 over the whole, or arranged in definite rows or sets, enabling the speci- 

 men to adopt a certain position, in merely stretching along any substance, 

 or adhering to it in the shape of a crescent or a cucumber. The suckers 

 of the Phantapus occupy the sides and the middle of a quadrangular 

 compartment on the lower surface : those of the middle extending in a 

 row of two lines to the ends of the quadrangle ; the others extending in 

 a double or triple row of suckers in a line just within the four sides of 

 the quadrangle. The whole compartment equals about a third of the 

 length of the specimen. 



As the animal adheres by the five rows of suckers occupying a por- 

 tion of the under surface, the two extremities are much elevated above 

 the plane of position. Plate XV. 



Thus very httle resemblance will be found between the form and 

 position of the Holotlmrin Phantapus and others of its genus. 



Some authors are dissatisfied with the name of suckers usually ap- 

 plied to the organs now referred to, desirous that they should be always 

 characterised as feet. No doubt they may be sometimes employed as 

 auxiliaries in progression, but their common and permanent office is to 

 secure the body of the animal by their adhesion to some solid substance. 

 They are occupied more as suckers than feet. I never saw the Phanta- 

 pus during progression, which is probably somewhat different from that 

 of the other species. 



This animal extends about seven inches from the tip of the tenta- 

 cula to the posterior extremity, when completely displayed. 



When contracted, and the arborescence concealed, it is considerably 



