PLANKTON OF THE GULF OF MAINE 223 



On July 10, 1913 (station 10062), it swarmed near the 100-meter contour off 

 Marthas Vineyard, and again on October 21 and 22, 1915, it occurred right across 

 the whole breadth of the continental shelf off Marthas Vineyard, most abundantly 

 near shore (see table, p. 298, stations 10331 to 10333), all of which proves it as wide- 

 spread out to the continental edge off southern New England as it is farther south. 



C. typicus has proved to be a decidedly more important member of the plankton 

 of the Gulf of Maine than is its relative, ft hamatus, as is described below; but Cape 

 Sable evidently marks the most northerly and easterly limit to its regular occurrence 

 along the North American coast line, for it does not appear in Willey's (1919) lists 

 of copepods collected on and along the slopes of the Nova Scotian and Newfoundland 

 Banks and in the intervening deeps. The Grampus did not find it between Cape 

 Sable and Halifax that same summer. It has not been reported from the Gulf of 

 St. Lawrence, nor did Herdman take it west of longitude about 28° W. on his two 

 traverses of the North Atlantic between Liverpool and the St. Lawrence River. 

 Comparison with the known range of C. hamatus shows ft typicus to be the more 

 southerly of the pair by about 7° of latitude, in terms of its northern boundary. 



Gulf of Maine. — When the locality records for C. typicus in the Gulf of Maine 

 are expanded to include Georges Bank 23 (fig. 70) there is no evident concentration in 

 the western side or in the eastern. 



It is reported from Plymouth Harbor by Wheeler (1901) and from St. Andrews 

 by Willey (1919); hence it would no doubt be found in similar estuarine situations 

 all along the intervening coastline. Apparently it is never plentiful as far east as 

 the shallows west of Nova Scotia and perhaps never reaches Browns Bank or the 

 eastern part of Georges, and one record close to land off Shelburne, Nova Scotia, 

 September 6, 1915 (station 10313), is, so far as I can learn, the most easterly known 

 outpost of the species on the Atlantic coast of North America. The preponderance 

 of records in the inner parts of the gulf, as contrasted with the basin, accords with 

 a nature more neritic than oceanic (p. 35). In fact, its distribution east and north 

 of Cape Cod closely parallels that of the hydromedusa Phialidium languidum p. 350) ; 

 but this applies only to the most northerly part of its range, for off southern New 

 England and thence southward it occurs generally right out to the continental edge. 



Seasonal fluctuations. — In its seasonal ebb and flow in the gulf, C. typicus closely 

 parallels C. hamatus. Thus it was so rare during the spring quarter, as exemplified 

 by the February to May cruises of 1920, that it was detected in only 6 out of 81 

 vertical hauls (about 7 per cent); it appeared in but one May haul in 1915 and not 

 at all in June. Furthermore, the numbers of specimens concerned have invariably 

 been small on the few occasions when C. typicus has figured in the spring lists. On 

 the western part of Georges Bank (February 23, 1920) it constituted 18 per cent of 

 the copepods, but the total number was so small that this percentage amounts to 

 only about 325 C. typicus per square meter. The maxima during the February to 

 June period arc 2,625 per square meter in the western basin on February 24, 1920 

 (station 20049), and 4,115 in the eastern basin on May 6, 1915 (station 10270, see 

 tables, pp. 297 and 299), with less than 300 per square meter at the few other stations 

 of record for these months. 



» Also dominant over northern and eastern parts of Oeorges Bank, at the surface, August 7, 1926. 

 75808—26 15 



