BATHYMETRTCAL RANGE. 



During the cruise of the Challenger, 196 species of Alcyonaria (excluding 

 Pennatulacea) were obtained. These may be grouped according to the depths from 

 which they were collected as follows : — 



From the above we see that the number of species lessens gradually from the surface 

 waters to the greater depths. 



The proportion between the number of species found in the first zone to the number 

 in subsequent zones would appear much increased, were we to include with the foregoing 

 species those previously recognised, which for the most part belong to this first zone. 



The character of the fauna in the first zone varies in the different seas and latitudes 

 examined, and more especially in the surface waters which are most exposed to climatic 

 influences. 



It is possible to distinguish a yet more littoral fauna, which extends to the level of 

 the low tide mark, from one extending into the deeper water. In the temperate and 

 cold seas there are only a few species in this littoral fauna, where inconspicuous forms 

 of Cornularidse, e.g., Cornularia, Clavularia, Sarcodictyon, grow on the rocks or cover 

 the surfaces of Zostera or of Algae. The only addition to these is a low growing 

 Alcyonium, or, as upon the east coast of America, a bushy Telesto. 



In the equatorial seas this zone is somewhat richer. In the West Indies and 

 Brazil the occurrence of the following has been ascertained : — Some Xenidse; among 

 the Alcyonidse, Ammothea ; among the Gorgonaceas, Scleraxonia, such as Briareum, 

 and among the Holaxonia, Plexaurella, Hymenogorgia, Gorgonia, Leptogorgia. 



