A REVIEW OF THE MYSIDACEA 183 



20+ specimens; H5211, 1 specimen; H5216, ? specimens; H5219, 

 4 specimens; H5228, 3 specimens; H5249, 1 specimen; H5255, 25+ 

 specimens; H5266, ? specimens; H5273, 35+ specimens; H5277, ? 

 specimens; H5298, 30+ specimens; H5299, ? specimens; H5301, 4 

 specimens; H5302, 6 specimens; H5303, 3 specimens; H5304, 1 speci- 

 men; H5305, 1 specimen; H5307, 1 specimen; H5310, 50+ specimens; 

 H5312, 10+ specimens; H5313, 10+ specimens; H5314, 25+ speci- 

 mens; H5321, 1 specimen; H5322, 2 specimens; H5328, % specimens; 

 H5337, 6 specimens ; H5338, 2 specimens ; H5339, 1 specimen ; H5341, 

 15 specimens; H5346, 4 specimens; H5347, 1 specimen; D5764B, 1 

 specimen; D5798, 8 specimens; D5803, 5 specimens; D5805, 2 speci- 

 mens ; D5822, 1 specimen. 



Distribution. — Pacific rim from San Francisco north and west to 

 northeastern Asia. 



Remarks. — The separate specific identity of Neomysis rayii Mur- 

 doch and N. franciscorum Holmes has always been a matter of some 

 doubt. Murdoch's original description was meager and made com- 

 parison with later material difficult. Holmes (1900) when describing 

 N. franciscorum said that it differed from N. rayii in having the telson 

 acute instead of truncate and in having more joints in the propodal 

 joint of the thoracic limbs. Hansen (1913b) showed that Holmes' 

 description of the telson of N. franciscorum as being acute was an error 

 and that it was in fact truncate and very similar to the telson of 

 N. rayii. An examination of the cotypes of Mysis rayii Murdoch, 

 shows that the thoracic limbs have about 20 joints in the propodus of 

 the endopod. The number of these joints increases with age, and 

 as Murdoch's specimens were as large as 65 mm. length the difference 

 between Holmes' specimens and his can be explained as due to age, and 

 the difference is negligible from a specific point of view. Hansen 

 ( 1913b) was inclined to regard N. rayii and N. franciscorum as distinct 

 species, differing in the length of the frontal plate, the proportions 

 of the eye, and the telson. The differences pointed out by Hansen 

 are small and such as may be accounted for by age and size. Never- 

 theless, in 1932 I agreed with Hansen's opinion and pointed out a 

 further difference between the species in the form of the fourth pleopod 

 of the male. In 1933, when recording TV. franciscorum from British 

 Columbia, I remarked that the specimens from the latter locality were 

 rather puzzling and appeared to be intermediate between N. rayii and 

 N. franciscorum, agreeing with the former in the character of the 

 telson and with the latter in the form of the fourth pleopod of the 

 male. 



The material here recorded provides a more or less continuous series 

 of specimens from the point of view of geographical distribution, 

 extending from 69° N. to 29° N., the biggest gap between 48° N. and 



893476 — 51 13 



