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 (Servos, strange; @pos, 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 Heteromz 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 Dallizde, one species is known, the 
Alaska blackfish, Dallia pectoralis. 
