A REVIEW OF THE MYSIDACEA 



85 



Nanaimo, collector Dr. Th. Mortensen, June 25 and July 10, 1915, 

 several hundreds of both sexes. 



Distribution. — The original material of this species was collected 

 in the Bering Sea and the present material includes four additional 

 records from that area. In addition there are records from British 

 Columbia and California so that the species is now known to occur 

 all along the Pacific coast of America from Alaska to California. 

 The specimens from California are unfortunately all females and 

 there are no males from which to substantiate the record. The speci- 

 mens are, however, so completely in agreement with Alaskan specimens 

 that, in the absence of males, I must include them in this species. 



Remarks. — The above description agrees very closely with that of 

 Czerniavsky, and in spite of some discrepancies I think there can be 

 no doubt of the identity of these specimens with Archaeomysis 

 grebnitzkii. The main points of difference concern the number of 

 joints in the pleopods, though the form of these appendages agrees 

 very closely with that described by Czerniavsky. In the female the 

 third pair of pleopods is described as having the exopod showing 

 division into three sub joints, and the endopods of the third and fourth 

 pairs terminating in minute joints, two in the third and one in the 

 fourth. I am unable to make out these structures in my specimens, 

 both exopod and endopod of all the pleopods consisting of a single 

 joint. 



In the male, while the general form of the pleopods is in close agree- 

 ment with Czerniavsky 's description, the numbers of joints in the 

 various exopods and endopods show some variation from his figures. 

 The differences are set out in table 7. I have not regarded these 

 differences as of specific value. 



Table 7. — Variation in numbers of joints in exopods and endopods in Archaeomysis 



grebnitzkii 



It is a matter of great interest that this species, which has so long 

 remained obscure, should have been rediscovered so that its structure 

 and affinities can be definitely established. Czerniavsky's original 

 description is substantially accurate and he justly realized the primi- 



