652 PROCEEDINOS OF THE NATIONAL MUSEUM. vol. 41. 



DIASTYLIS RATHKU (Krjlyer). 



Cuma rathJcii Kr0yer, Naturh. Tidsskr., vol. 3, 1841, p. 513, pis. 5, 6, figs. 17-30. 



Diastylis rathkii S. I. Smith, Trans. Conn. Acad., vol. 5, 1879, p. 107 (with synon- 

 ymy).— G. 0. Sars, Crust. Norway, vol. 3, 1900, pp. 44 and 107, pis. 33, 34, 

 70-72. — ZiMMER, Die arktischen Cumaceen, in Roraer u. Schaudinn, Fauna 

 Arctica, vol. 1, Lief. 3, 1900, p. 423. 



Diastylis rathkii, var. Murdoch, Rep. Int. Polar Exp. Pt. Barrow, Alaska, 1885, 

 p. 142. 



Diastylis rathkii, var. glabra Zimmer, Die arktischen Cumaceen, in Romer u. 

 Schaudinn, Fauna Arctica, vol. 1, Lief. 3, 1900, p. 424. 



Diastylis rathkii, var. sarsi Norman, Ann. Mag. Nat. Hist., eer. 7, vol. 10, 1902, 

 p. 478. 



A lengthy, though not exhaustive, hst of references to literature 

 is given by Zimmer.^ 



The specimens wliich I refer to this species show a considerable 

 range of variation, especially as regards the spiniilation of the cara- 

 pace, but there is no evident discontinuity to justify the separation 

 of named varieties. It would be possible to select a series of speci- 

 mens leading by small gradations froin the perfectly smooth forms 

 (var. glabra Zimmer) to some that are even more spinous than that 

 figured by Sars ^ and named var. sarsi by Norman. Spiny and 

 smooth individuals sometimes occur in the same gathering, and it is 

 perhaps worthy of note that immature males generally, perhaps 

 always, have the dorsal spinules conspicuously developed even when 

 they accompany females of the smooth type. As only a very small 

 number of adult males are in the collection I am not able to say 

 whether noteworthy variations occur in this sex. The specimens 

 examined do not differ perceptibly from that described by Sars and 

 attributed to the var. sarsi of Norman. 



This species has not hitherto been recorded from the North Pacific, 

 although Stuxberg traced it along the northern coasts of Asia as far 

 as the East Cape, and Murdoch has recorded specimens of the smooth 

 type from Point Franklin on the east side of Bering Strait. The 

 present collection contains specimens from various locahties on the 

 coast of Alaska and the Aleutian Islands and as far south as Sitka. 

 On the Atlantic coast of North America the species does not appear 

 to have been recorded south of Halifax, Nova Scotia. The list of 

 locahties given below carries it as far south as latitude 41° 11' N. at 

 a depth of 499 fathoms. The species is known from a depth of 649 

 fathoms (Norwegian North Atlantic Expedition). 



Localities. — Godhavn, Greenland; Ensign C. S. McClain, June, 

 1884; U.S.N.M. 13774; 1 female. 



Off Battle Harbor, Labrador; 50 fathoms; Owen Bryant, Sep- 

 tember, 1908; U.S.N.M. 44086; 1 female. 



' Fauna Arctica, vol. 1, p. 424. s Crust. Norway, vol. 3, pis. 70-72. 



