REPORT ON THE TUNICATA. 



269 



From this table it is a simple matter to determine the range in depth of any 

 particular genus, e.g. : — 



Molgula . extends from 2 to 600 fathoms. 



Styela . 2 to 2600 „ 



The four families of Ascidiae Simplices are found to have the following limits : — 



The Molg-ulidaa range from the shore to 600 fathoms. 

 The Cynthiidaa „ „ 2600 „ 



The Ascidiidse 

 The Clavelinidao 



2600 

 L29 



Hence it appears that there is no family peculiar to deep water, as inch of the four has 

 species ranging from a few fathoms of water downwards. The Clavelinidae have as yet 

 not been found at a depth greater than 129 fathoms, and most of the species inhabit much 

 shallower water. If Ecteinascidia crassa be excepted, the Challenger specimens of the 

 Clavelinidas are all from less than 20 fathoms. 



The MolguhVhe are represented in the abyssal zone 1 by Molgula pyriformis, at 600 

 fathoms, while the remaining species range between shallow water and 150 fathoms. 



The Cynthiidse and Ascidiidse have both a much wider distribution in depth, and 

 each of them contains genera whieli are peculiarly abyssal. In the Cynthiidae the sub- 



1 500 fathoms and upwards. 



