A REVIEW OF THE MYSIDACEA 187 



NEOMYSIS MERCEDIS Holmes 



Figure 72 



Neoniysis mercedis Holmes, 1897, p. 199, pi. 19 ; 1900, p. 222.— Tattersaix, 1932b, 

 p. 318, figs. 39-^1 ; 1933, p. 11. 



Occurrence. — West coast of the United States: Waddell Creek 

 Lagoon, Calif., tide out and water fresh at the time, November 4, 

 3932, 2 immature; South Channel, Grays Harbor, Wash., 1 male, 10 

 females, all immature; Carr Inlet, Puget Sound, Wash., 4 adult males, 

 1 immature, up to 15 mm. During the survey of San Francisco Bay, 

 by the Albatross, 1912-13, specimens were collected at the following 

 stations: H4991 and H5106, 3 specimens; H5084, 6 specimens; H5085, 

 15+ specimens; H5090, 30+ specimens; H5110, 300+ specimens; 

 H5113, 1 specimen; H5136, 1 specimen; H5137, 1 specimen; H5147, 1 

 specimen; H5151, 1 specimen; H5166, 15+ specimens; H5172, 1 speci- 

 men; H5177, 9 specimens; H5184, 1 specimen; H5288, 6 specimens; 

 H5291, 6 specimens; H5292, 6 specimens; H5302, 1 specimen; H5304, 

 1 specimen ; D5761B, 1 specimen ; off Red Rock, San Francisco Bay, 

 March 22, 1912, 1 specimen. 



Distribution. — N. mercedis has been recorded from Lake Merced, a 

 fresh-water lake on the San Francisco Peninsula, Calif. (Holmes, 

 1897) ; San Francisco Harbor (Tattersall, 1932b) ; Vancouver Island 

 (Tattersall, 1933) ; Washington; Oregon. 



Remarks. — N. mercedis is very closely related to N. intermedia 

 (Czerniavsky ) , and to N. awatschensis (Brandt) . It differs from the 

 former in the following points : 



(1) The antennal scale (fig. 72, a) is relatively shorter and broader, 

 8 times as long as broad, whereas in N. intermedia it is 10 times as 

 long as broad. 



(2) In the proportions of the joints of the outer branch of the fourth 

 pleopod of the male (fig. 72, c). In .V. mercedis the terminal joint is 

 less than one-quarter of the length of the proximal joint and is shorter 

 than the terminal setae. In N. intermedia the terminal joint is half 

 as long as the proximal and is longer than the terminal setae. In all 

 other particulars the two species agree very closely. 



N. mercedis differs from N. aioatschensis in the following points: 



(1) In size. N. awatschensis is 10 mm. when adult and N. mercedis 

 reaches 15 mm. 



(2) In color. N. aioatschensis is black and N. mercedis is certainly 

 not black. 



(3) In the rostral plate. That of N. awatschensis is pointed, while 

 that of N. mercedis is broadly quadrangular in shape. 



(4) In the sixth joint of the thoracic endopods, which in N. 

 aioatschensis has only 3 to 6 subsidiary joints, in N. mercedis 8 to 10. 



