R otatoria E 13 



Diurella collaris (Rousselet) . 



Collected by Jessup from lakes on Old Crow river flats, 40 miles north of 

 c\ T ew Rampart House, on July 3, 1911. 



Diurella cavia (Gosse). 



A few specimens in Jessup's collections from a pond near New Rampart 

 House, at the International Boundary and Porcupine river, on June 12, 1911. 



FAMILY SYNCILOTID/E. 



Synchaeta oblonga Ehrenberg. 



Abundant in collections made from the lake at Bernard harbour by Johansen 

 on May 6 and 7, 1916; same lake south of Bernard harbdur, May 21, 1916. 



Synchaeta johanseni, new species. 

 Plate 1, fig. 3. 



The body is fairly slender, bell-shaped and very transparent. Its greatest 

 width, about mid-length, is one third of the total length. The foot is well 

 marked off from the body, large at the base and tapers gradually to the very 

 small toes ; its length is one fourth of the length of the body. The head is tri- 

 angular and the auricles powerful; on the median line, between the anterior 

 pair of tactile bristles, there is a tubular sensory organ as in S. vorax Rousselet. 

 The dorsal antenna is in the normal position; the lateral antennae are near the 

 posterior end of the body and well towards the ventral side; they are slender 

 tubules, armed with a minute tuft of setae. The foot glands are very small. 

 The form and position of the eyespot could not be made out from the preserved 

 material. 



Total length 350 ju; width of body at mid-length 120 ju; length of foot 

 70 //; length of toes 7 ju- 



This species occurred in large numbers in a surface collection made by F. 

 Johansen on August 23, 1914, at station 36, off Cape Lyon, in Amundsen gulf. 



Synchaeta johanseni is closely related to S. vorax Rousselet, from which it 

 differs in the more slender body, longer and stouter foot, very small foot glands 

 and minute toes, as well as in the position of the lateral antennae. Its presence 

 in Amundsen Gulf is of the greatest interest, as up to the present only two species 

 of rotifers, Synchaeta atlantica and Trichocerca ( = Rattulus) henseni, are known 

 from oceanic waters; these were both found by Zelinka in the collections of the 

 German Plankton Expedition from the Atlantic ocean, south of Iceland. While 

 it would perhaps be incorrect to call Amundsen Gulf an ocean, the conditions 

 where the collection was made are oceanic, at least as far as salinity and absence 

 of admixture of fresh water are concerned; there are no rivers of any consider- 

 able volume discharging near Cape Lyon, and Mr. Johansen informs me that 

 few of the rivers flowing into the Arctic ocean carry much water in the summer. 

 How to account for the presence of this rotifer at a single station and its absence 

 everywhere else is a problem for which no solution can be offered; it may be 

 noted that the collection contained virtually no other zooplankton, and it is 

 possible that the absence of enemies may be an important factor in the main- 

 tenance of this rotifer in such a circumscribed area. 



Filinia longiseta (Ehrenberg). 



Triarthra longiseta HUDSON and GOSSE, Rotifera, 1886, vol. 2, p. 6, pi. 13,fig.6. 



Collected by Johansen in a brackish lagoon west of Martin point, Alaska, 

 on July 28, 1914; lake south of Bernard harbour, November 28, 1915; on May 

 6, 7, and June 12, 1916. 



