KOFOID AND SWEZY: UNARMORED DINOFLAGELLATA 95 



and Ceratium ranipes. Others are rather closely restricted to coastal waters 

 and the ueritic fauna, as, for example, ExuviaeUa, Prorocentrnm, NoefUuea, 

 and Ccratiiim divaricatuni. 



In A-iew of the fact that representatives of this order have adapted them- 

 selves to salt, brackish and fresh waters and even to a parasitic mode of life, 

 it is rather to l)e expected tliat they will he found in other available habitats 

 as well. 



The beach sands of the littoral zone offer such a lial)itat and one, moreover, 

 which is constantl,v invaded by coastal waters laden with the neritie fauna. 

 Whenever the tidal amplitude and the breakers come into play we find an 

 automatic agency for the incessant stranding of the dinoflagellates of the neritie 

 zone u])on the surface and in the interstices of the beach sands. As each re- 

 current tide or breaker recedes the sand acts as a filter bed upon which is accum- 

 ulated the plankton of the infiltrating water. This accumulating action of the 

 beach sands is especially noticeable along the California coast whenever the 

 outl)reaks of "]'od water" due to dinoflagellates occur. At such times the l)eaeh 

 becomes highly phospliorescent with its accumulating, but still li\-iug Goniimilax, 

 and becomes luminous whenever disturbed by the breakers or by passing foot- 

 steps. 



A typical sand beach form is foimd in the genus AnrpJiidinmm, some of the 

 members of which have not been recorded thus far from any other habitat. 

 The occurrence of two or more species of this genus has been recorded by 

 Herdman (1911, 1912, 1913), who followed for several years their recurrence 

 on the beaches of the sheltered harbor at Port Erin, Isle of Man, in the Irish 

 Sea. According to him, these species form a yellowish brown film, rii)pled by 

 tidal movements, on the surface of the sands in April, September, October, and 

 November, almost to the exclusion of diatoms, which abound at other times. 

 These organisms were abundant from one day to two or even three weeks, after 

 w]ii(4i they almost completely disappeared. Although abundant on the sands 

 witliin tidal limits, these species could not l)e detected in the plankton of the 

 immediately contiguous waters. 



An examination of the arenaciphilous microfauna and flora at La Jolla also 

 reveals a numl^er of species which have not been observed in the hauls made 

 concurrently a short distance offshore, nor have they been discovered in the 

 pelagic collections made prior to or since these examinations. These exami- 

 nations were made by rinsing the sands cautiously in fresh sea water, condens- 

 ing the organism released thereby on filter paper, and examining the sediment 

 thus collected. In addition to the representatives of the neritie plankton, of 

 which a few stranded individuals were always present, there appeared to be 

 an indigenous complex consisting of a few species of naviculoid diatoms, some 

 small nematode worms and several s])ccies of dinollageUates. 



The dinoflagellates discovered in this complex were mainly members of the 

 genus Amphidinium, as follows: Aniphidiiiiiiiii (isi/iiiuu'tricmn,A. corpulentum, 



