568 PROCEEDINGS OF THE NATIONAL MUSEUM vol. iis 



Samples reported here represent only a small part of such habitats 

 in the entire Cape Thompson region. Most are from the marshy area 

 near Singoalik Lagoon and are characterized as pools because of their 

 intermittent nature and small size. Many are shallow, ranging from 

 only 15 to 30 cm. in depth but some have a maximum depth of about 

 1 meter. Those near Singoalik and Mapsorak Lagoons are considered 

 as more or less brackish; precise salinity records associated with the 

 collections are not available but other records indicate that they are 

 not continuously fresh. Salinity undoubtedly varies with the fluctu- 

 ating water level which may be considerable both during a season and 

 from one year to another. 



Records are summarized by year of collection in table L Excepting 

 Pool 1, the pools from which collections were made in 1961 were not 

 correlated with any of the previous year, and it is not known which 

 correspond to the pools listed for 1960. Copepodid stages are listed 

 for each date. In no instance do the collections furnish adequate data 

 for life cycle studies, but they do emphasize the value of the locale for 

 such studies. Of particular interest is the question of whether such 

 populations of Eurytemora, unlike most other calanoids of continental 

 bodies of water on the Arctic Slope, produce more than one generation 

 a year (Wilson and Tash, MS.) . The copepodid stages present in the 

 series of 1960 collections in Pool 1 (table 1) suggest two generations of 

 E. gracilicauda. Absence of any specimens in the middle of the season 

 may have been due to the presence of the species only as naupliar 

 stages which collecting gear failed to sample. Production of two 

 generations in a season would undoubtedly be dependent upon early 

 melting of snow and ice in the region, as probably happened in 1960 

 when adults bearing ovisacs were collected as early as June 29 (see 

 discussion under E. arctica, p. 567). As with E. gracilicauda, the 

 records of E. canadensis in shallow pools that freeze to the bottom, 

 not only in the Cape Thompson region but in other parts of its dis- 

 tributional range, suggest overwintering of the species as resting eggs. 



Coastal Lagoons | 



Including those studied by Johnson in 1959, a total of 11 lagoons 

 has been surveyed. As Johnson (1961) indicated, they group natural- 

 ly into those lying north and south of Cape Thompson, and the}^ are 

 summarized here by these geographic subdivisions (table 2). They 

 are dish shaped in profile, range in length from 3.2 to 8.0 km., are 

 shallow (maximum depth, 3 meters), and are free of ice cover for 

 about 2)2-3 months. Most do not now have direct connections with 

 the sea. Maximmn temperatures recorded in 1960 were 13.7° C. on 

 July 18 for Mapsorak Lagoon and 16.2° C. for Pusigrak Lagoon. 



