A REVIEW OF THE MTSIDACEA 109 



deep-water race also has a similar distribution, though in much deeper 

 water, for specimens in the above list of records, measuring up to 37 

 mm., were found all along the coast from Alaska to California. An 

 examination of these records does suggest that northern specimens of 

 the deep-water race tend to be larger than the southern and that the 

 species tends to get into deeper water in more southern latitudes. The 

 average size of adult specimens from Alaska is 37 mm., and from Cali- 

 fornia only 32 mm. The average depth of the Alaska stations is 300 

 fathoms, and of the California stations 406 fathoms. The evidence is 

 not conclusive since, though there are over 150 specimens, they were 

 collected over a very wide area and the number of adult specimens 

 from any one locality or area is not large. 



Ii (1937, p. 200) has described a new species of the genus, H. affinis, 

 from Japan. It is separated from H. anomala on three characters : 

 (1) The shape of the third joint of the antennal peduncle; (2) the 

 presence of small epipodial processes on the basal joint of the endopods 

 of the third to the eighth thoracic limbs; and (3) the form of the 

 endopod of the fourth pleopod of the male, which is only slightly 

 longer than the exopod and does not have the greatly elongate distal 

 joints found in H. anomala. Of these differences the second disap- 

 pears in the light of the present specimens in which epipodial processes 

 are present on the endopods of the third to the eighth thoracic limbs. 

 The other two characters would appear to be distinctive. Ii's speci- 

 mens measured 15 mm., and at first sight it appeared as if H. affinis 

 could be regarded as a smaller coastal race of H. anomala occurring 

 off Japan, similar to the smaller coastal race occurring off the west 

 coast of America. The difficulty of so regarding it lies in the form of 

 the fourth pleopod of the male. In the American coastal race this 

 appendage is in every way similar to the same appendage of the large 

 deep-water race and, moreover, I have shown above that even in 

 immature specimens the general plan of the adult pleopod is laid down. 

 The fourth pleopod of the male of H. affinis is quite different from the 

 same appendage in H. anomala, even of immature specimens. The 

 latter species does occur off the coasts of Korea, as evidenced from the 

 specimen recorded above from Albatross station 4861, which was a 

 female measuring 34 mm., which I could not distinguish from 

 H. anomala. Ii unfortunately does not give the depth at which his 

 specimens were taken. 



