432 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 115 



important because of the overlap of the range of the closely alhed form 

 B. longidactylus Lockington (1877) in California. These two species, 

 as well as B. ensenadensis Glassell (1938) of southern CaUfornia and 

 Mexico, are figured and redescribed here in some detail. 



In the 1870's W. N. Lockington and J. S. Kingsley each described 

 two species of hooded shrimps from California. They engaged in 

 considerable controversy in their papers as to whether or not Betaeus 

 was a valid genus, and occasionally they referred species of Betaeus 

 to the genus Alpheus; as a result, in the literature both Alpheus and 

 Betaeus are used in referring to these shrimps. Lockington (1877b, 

 1878) described two species briefly, without figures, and, unfortunately, 

 named one Betaeus equimanus, a name that had been used previously 

 by Dana (1852, p. 560; 1855, pi. 35) for a shrimp from New Zealand. 

 Early in 1878 Kingsley published a description of apparently the 

 same shrimp and called it Alpheus harfordi but indicated that if 

 "aequimanu^'^ should prove to be different, the shrimp would have to 

 be called ''aequalis.'' Later in the same year Lockington called it 

 B. egualis and enlarged his description by incorporating Kingsley's 

 description of B. harfordi. He was convinced that they were identical 

 but because of his use of a preoccupied name, he lost the honor of 

 naming the species. Betaeus harfordi (Kingsley) is therefore the 

 valid name. 



Holmes (1900) gave a description with more details than those 

 given by the early writers, but unfortunately he added new habitats 

 that perhaps have helped to mask the presence of four distinct forms: 

 two commensal and two free-living. 



In 1934 several hooded shrimps were taken in tide pools on the west 

 coast of Vancouver Island by E. G. Hart. These agreed mth pub- 

 lished descriptions of B. harfordi except for a few minor differences. 

 Since shrimps of the family Alpheidae often show considerable vari- 

 ation in relative proportions according to age and sex, no suspicion of 

 significant differences arose until individuals from California were 

 compared with the northern specimens. As a result of a detailed 

 comparative study, it now seems that those found commensal within 

 the mantle cavity of abalones are referable to B. harfordi and that 

 the remainder represent three undescribed species. The similar, but 

 quite distinct, form that lives in association with sea urchins I propose 

 to call B. macginitieae in recognition of Nettie MacGinitie, who, with 

 her husband Professor G. E. MacGinitie, has contributed so much to 

 our knowledge of the genus. For the two free-hving forms I have 

 chosen the names B. gracilis and B. setosus. 



In view of the fact that the published descriptions and figures of 

 the known species are inadequate, an attempt is made herewith to 

 supplement them with more detailed descriptions and illustrations. 



