BIGELOW: COAST WATER EXPLORATION OF 1913. ' 333 



Barnegat (Stations 10060 to 10068) ; but it was absent at the more 

 southern stations, nor was it found over the outer part of the shelf 

 south of Long Island (Stations 10063, 10065). And tripos invariably 

 outnumbered it in the hauls south and west of Cape Cod. On our 

 coasts, at least in summer, longipcs evidently belongs to northern water. 

 The salinity in which it was living (on the surface, where all the hauls 

 with the # 20 silk net were made) ranged from 31.8%o (Station 10104) 

 to 33.4%o (Station 10061); the temperature from 48° (Station 10095) 

 to 69° (Station 10069). But it was far less abundant at temperatures 

 above 62° or 63° than in the colder water of the Gulf: — for example 

 at Station 10061, surface temperature 68°, only two specimens were 

 detected; Station 10062, 67°, only an occasional specimen; Station 

 10069, 69°, only one specimen was found. 



Ceratium tripos was taken at practically all our southern stations, 

 as well as north and east of New York and in the Gulf of Maine, and 

 at Stations 10063, 10065 over the outer part of the shelf where longipes 

 was absent. At only three Stations have I failed to find it in the 

 plankton, viz., 10075, 10076, 10078, all of them within the influence 

 of Chesapeake Bay water (p. 200). 



A third species of Ceratium, C. macroceros, easily distinguished by its 

 very long, slenfler horns, occurred in the hauls at the southern stations. 

 The most northerly records are Stations 10062, 10063, and 10083. 

 East of Barnegat it was greatly outnumbered by tripos (Stations 10062, 

 10063, 10065, 10067, 10069, 10083). South of this, where longipcs was 

 not found, r^iocrocero^ was always as numerous as tripos, the two species 

 being, roughly, equal at Stations 10073, 10074, 10077, 10079, 10082. 

 At Stations 10070, 10071, 10072, macroceros outnumbered tripos. 

 Ceratium macroceros was living at a very wide range of salinity, as 

 much so, even, as tripos (31 .3%o to 35.2%o) ; but its temperature range 

 was considerably less, the records all being from water warmer than 

 63° (63° to 77°) ; it was only once found in water cooler than 67°, and 

 then only an occasional specimen (Station 10067). And at only three 

 Stations (10062, 10067, 10069) were both longipes and macroceros taken 

 in the same haul. If the former belongs to boreal plankton, the lat- 

 ter is as certainly limited to warm water along our coasts. 



A fourth species of Ceratium, C. fusus, plays a subordinate role. 

 It has been found at twenty-seven stations, including the Gulf of 

 Maine as a whole (Stations 10057, 10058, 10086-10090, 10092, 10093, 

 10096, 10097, 10099, 10102-10104), and the continental shelf south 

 and west of Cape Cod (Stations 10061-10063; 10067-10070; 10073, 

 10074, 10077-10081). The only regions where it was notably absent 

 were in the Gulf Stream water (Station 10071); and in localities 



