DISTRIBUTION OF ROLOTHURIANS. 



135 



body ends in a long, tail-like prolongation ; C. arenata 

 Stimpson has fifteen four-pronged tentacles j it is com- 

 monly thrown up on the beaches 

 of Massachusetts Bay. A deep- 

 water form, a member of the 

 abyssal fauna, is Molpadia tur- 

 gida Yen-ill, which we have 



Fig. 91. Hooks and plates of 

 Synapta Girardii. After Verrill. 



dredged in over one hundred 



fathoms in the Gulf of Maine, 

 and which ranges southward to 

 Florida. It has a head-end like 

 the neck of a bottle, and the end of the body suddenly con- 

 tracts into a tail, with a very small anus. There are fifteen 

 tentacles. 



Order 2. Pedata, or Holothurians with feet. The mem- 

 bers of the first family (DendrocMrotcB) have tree-like, 

 branching tentacles, retractor muscles, without Cuvierian 

 organs. It is represented by Thy one and Pentacta, while 

 here belong also Lophothuria Fabricii Diiben and Koren, 

 Psolus phantapus and P. squamatus, in which the body is 

 armed with heavy calcareous plates, and the feet are confined 

 to a ventral creeping disk. 



In the highest family, Aspidochirotoe, there are tentacular 

 ampullse ; the left respiratory tree is bound to the body- 

 walls, and there is a single ovary, while Cuvierian organs 

 are present. Holothuria is the type of the group. H. edulis 

 Lesson, of the Moluccas and Australia, and H. tremula 

 forms, when dried, the trepang sold in Chinese markets. 

 Our H. floridana has been dried and exported to China as 

 an article of food. 



In their geographical distribution the Apoda are mostly 

 boreal and arctic. Of the Pedata, the Dendrochirotce are 

 mostly northern or arctic, while the highest group, Aspi- 

 dochirotce, are mainly tropical. Certain genera (Holothwria t 

 Thyone, Psolus,Pentacta, Chirodota, and Synapta) are almost 

 cosmopolitan. 



A few forms attain a great depth, and certain abyssal 

 forms are often highly colored. One species, Synapta 



