PLANKTON OF THE GULF OF MAINE 



131 



they are lifted by active vertical currents. The glass shrimps (genus Pasiphrea) are 

 the only decapods regularly planktonic in the Gulf of Maine when adult. 



Pasipheea 



These shrimps are so much larger (80 to 90 millimeters long when adult) than 

 any other crustaceans pelagic in the gulf that even a single specimen is sure to be 

 detected in the tow. It is therefore safe to assume that the list presented herewith 

 comprises our whole catch, which is not true of smaller organisms easily overlooked 

 in the mass of other plankton unless abundantly represented in the catch. 



We towed our first glass shrimps (three in number) in the western basin in a 

 haul from 150 meters on August 9, 1913 (station 10088). Since then they have been 

 taken there on August 22, 1914; August 31, 1915; March 5, 1920; and April 18, 1920 

 (stations 10254, 10307, 20087, and 20115), and likewise at two stations in the deep 

 water in the northeastern part of the gulf (March 3, 1920, station 20055, and March 

 22, 1920, station 20081) ; once in the southeast corner (April 17, 1920, station 20112), 

 and once at the outer edge of the shelf off Cape Sable (March 19, 1920, station 20076). 



So far as I can learn, the only previous records of this genus for the Gulf of 

 Maine are as follows: Western Basin, approximate latitude 42° 38', longitude 69° 

 38', two specimens dredged in 203 meters in August, 1877; two more near the same 

 locality, 256 and 311 meters (dredge), on August 27, 1878 (Smith, 1879); others from 

 Cape Cod Bay and from off Cape Cod, 25 meters and 212 to 223 meters, respectively 

 (Rathbun, 1905). 



These early captures were recorded as Pasiphxa tarda, which has long been 

 spoken of as the characteristic northern representative of the genus (Wollebagk, 

 1908). Sund (1913), however, has more recently shown that at least three perfectly 

 distinct and easily recognizable species have been confounded under this name, 

 Smith's own illustration (S. I. Smith, 1879, pi. 10, fig. 1) showing that in reality 

 the early American records were not based on tarda but on the P. multidentata of 

 Esmark, which has also proved to be the commonest glass shrimp in Norwegian 

 waters. 69 All the recent specimens from within the Gulf of Maine likewise are 

 multidentata, a perfectly transparent species, whereas P. tarda is commonly blood 

 red. Our records of P. multidentata have been from comparatively deep hauls, 

 though not invariably from the deepest stratum in the Gulf (fig. 47) as follows: 



So far as I can learn, Pasiphrea has never been taken on the surface or in 

 plankton hauls shoaler than 75 meters in the Gulf of Maine, though it has been 

 dredged in as shallow water as 25 meters; hence, it is clearly bathypelagic in the 



• 9 The several species are easily separable by the form of the rostrum, which is high and coniform in multidentata. 

 I refer the reader to Sund (1913). 



For details 



