1912" 



The Glass Shrimps (Pasiphæa) in Northern Water! 



15 



This species was described by Keøyer in 1845, and was ap- 

 parently not recaptured until about 11 years ago, when the "Michael 

 Sårs" took several specimens in the Skagerack, which agree well 

 with Krøyer's description and with the figures drawn from Krøyer's 

 specimens in Gaimards "Voyage". This summer I had the oppor- 

 tunity of examining the single 

 survivor of these specimens 

 and was not able to detect 

 any important difference be- 

 tween it and the Skagerack 

 specimens, nor between these 

 and the specimens caught by 

 the Danish vessels "Ingolf" 

 and a Tjalfe" in the seas around 

 Greenland and Iceland. 



The separation of this 

 form from P. multidentata 

 needs no apology, as proved 

 by the figures which I take 

 the liberty of reproducing here 

 as pl. II, III from the rare 

 and textless work, Gaimards 

 "Voyage en Scandinavie 

 etc", and also the drawing 

 by Wollebæk (1908) from a 

 large Skagerack specimen,pl. I. 



Fig. 8 gives some details 

 from a Skagerack specimen 

 about 10 cm. in length (C = 

 32 mm.). 



Much closer are the rela- 

 tions between this speciés and 



P. principalis. The chief distinctions depend upon the form of the 

 rostrum and upon the relative size of the abdomen, as will be noticed 

 from an inspection of the digram fig. 3. 



The two forms agree in the shape of the scaphocerite, though 

 the apical spine is as a rule more developed in P. tar da; they also 

 agree in the armament of the 2nd pereiopod. It would seem 

 therefore that there is little ground for establishing two species, 

 but that is the only way to do justice to the differences which do 



Fig. 9. a — f Pasiphæa principalis, g—n 

 P. tarda. The figures inscribed below the 

 letters denote the size of the specimen 

 (C, i. e. : lateral length of carapace) in mm. 



