Fishes of the Western North Atlantic 437 



Eagle Rays of this genus appear to feed exclusively on the bottom, chiefly if not 

 entirely on the larger Crustacea and on hard-shelled mollusks, both univalve and bivalve. 

 They are described as swimming along the bottom until they encounter the currents of 

 water expelled by the siphons of clams, which they dig out by flapping their pectoral 

 fins and then crush with their millstone-like teeth. Indeed, they are so destructive to 

 clam beds in San Francisco Bay, California, that the local species {Myliobatis californicus) 

 is "the object of special exterminating parties by sport fishermen. "1^ But neither of the 

 western Atlantic species of the genus is plentiful enough to be a menace to shellfish beds. 



Range. Rays of this genus are widely distributed in tropical to warm temperate 

 continental waters; from northern Argentina to southern New England in the western 

 Atlantic; from South and Southwest Africa to southern Great Britain, less commonly to 

 Scotland, and occasionally to southern Norway, in the eastern Atlantic, including the 

 Canaries, the Azores, and the Mediterranean ; the Indian Ocean in general from Bay of 

 Bengal" south to Madagascar, Reunion, and South Africa; Australia, Tasmania, and 

 New Zealand; the western Pacific north to Japan and Korea; the west coast of North 

 America from northern California (Cape Mendocino) southward to Lower California; 

 also Peru, and perhaps Chile. 



No representative of the genus, as defined here, has been recorded from the East 

 Indies, so far as we can learn, or from any of the island groups of the middle or western 

 tropical Pacific. But it is more probable that they have been overlooked in these waters 

 than that their range fails to include them. The bathymetric range actually recorded 

 thus far for Myliobatis extends from the surface down to about 60 fathoms. 



Species. Recent surveys of the genus, as here defined,^' recognize three species in 

 the Atlantic and seven or eight in the Pacific and Indian oceans, besides one problemat- 

 ical form, described as lacking a dorsal fin," which has never been seen since it was first 

 recorded. 



The three Atlantic species, M. aquila (Linnaeus) 1758 of the eastern side, M. 

 freminvilUi Lesueur 1824 and M. goodei Garman 1885 of the western side, form an 

 extremely homogeneous group. But our own examination of the specimens listed else- 

 where has convinced us that the two American forms are separable by the various dif- 

 ferences stated under Distinctive Characters given for each (pp. 439, 446). Minor dif- 

 ferences also appear to separate both members of this pair from M. aquila (see Key to 

 Species, p. 438). But final decision on this point must await comparison (especially of 

 M. goodei) with more extensive series from the eastern Atlantic i» than we have seen. 



M. californicus Gill 1865 from California and Mexico parallels M. freminvilUi in the 

 position of the dorsal fin close behind the rear limits of the pelvics, but it resembles 

 M. goodei and M. aquila more nearly in the small size of its dorsal and in the shortness 



15. Walford, Fish Bull. Sacramento, 4;, 1935: 61. 



16. Jenkins (Fish. Brit. Isles, 1925: 342) reports taking Myliobalis frequently in the Bay of Bengal. 



17. Garman, Mem. Harv. Mus. comp. Zool., 36, 1913: 428; Fowler, Bull. U. S. nat. Mus., 100 (13), 1941: 458, as 

 Holorkinus. 



18. Myliobatis rhombus Basilewsky, Nouv. Mem. Soc. nat. Moscow, 10, 1855: 250; Pekin. 



19. We have seen only two small specimens of M. aquila. 



