206 The Scyphophori, Haplomi, and Xenomi 



to account for its wide distribution in the rivers of the southern 

 hemisphere. 



Neochanna is an ally of Galaxias living in burrows in the 

 clay or mud like a crayfish, often at a distance from water. As 

 in various other mud-living types, the ventral fins are obsolete. 



Order Xenomi. We must place near the Haplomi the 

 singular group of Xenomi (Zeros, strange; GOJJO?, shoulder), 

 regarded by Dr. Gill as a distinct order. Externally these fish 

 much resemble the mud-minnows, differing mainly in the very 

 broad pectorals. But the skeleton is thin and papery, the two 

 coracoids forming a single cartilaginous plate imperfectly divided. 

 The pectorals are attached directly to this without the inter- 

 vention of actinosts, but in the distal third, according to 

 Dr. Charles H. Gilbert, the coracoid plate begins to break up 



FIG. 164. Alaska Blackfish, Dallia pectoralis (Bean). St. Michaels, Alaska. 



into a fringe of narrow cartilaginous strips. These about equal 

 the very large number (33 to 36) of pectoral rays, the basal 

 part of each ray being slightly forked to receive the tip of the 

 cartilaginous strip. 



" In the deep-sea eels of the order Heteromi there is a some- 

 what similar condition of the coracoid elements inasmuch as 

 the hypercoracoid and hypocoracoid though present are merely 

 membranous elements surrounded by cartilage and the acti- 

 nosts are greatly reduced. It seems probable that we are 

 dealing in the two cases with independent degeneration of the 

 shoulder-girdle and that the two groups (Xenomi and Heteromi) 

 are not really related. ' ' (Gilbert. ) 



Of the single family Dalliidcc, one species is known, the 

 Alaska blackfish, Dallia pectoralis. 



