MAILED TUBEMOUTHS. 
423 
In the single dorsal tin the spinous portion usually exceeds the soft in extent; the 
anal tin having three or more spines, and its rayed portion being similar to the 
soft dorsal. The jaws are provided with small teeth, hut the palate is smooth; 
and the number of gills is four* In some species the teeth are lobate and the 
intestines complicated by many foldings; these types being vegetable-feeders 
while all the remainder are carnivorous. Among the best known representatives 
of the typical genus Chromis is the so-called butti of the Nile (0. niloticus), which 
is one of the largest members of the family; while Tristram’s cliromid ( Ctristrami ) 
here figured is from salt and other lakes in the Sahara and Ashanti. As a genus, 
Chromis is distinguished by its lobate teeth, the presence of only three spines in 
the anal fin, and the scaly gill-cover; and it therefore belongs to the vegetable¬ 
feeding group. Nineteen existing genera have been described; and the family 
appears to be represented by one, or perhaps two extinct generic types from the 
middle Eocene of Monte Bolca, in Italy. 
The Tuft-Gilled and Comb-Gilled Fishes, —Suborders 
Lophobranchii and Plectognathi. 
The two small subordinal groups of fan-finned fishes now to be noticed 
have been generally placed after the soft - finned fishes, but from recent 
investigations into their anatomy it appears more probable that they are highly 
specialised types related to the spiny-finned group. 
The Mailed Tube-Mouths, —Family Solenostoma tidje, 
A few small fishes from the Indian Ocean constituting the genus Solenostoma 
are the sole representatives of the first family of the suborder Lophobranchii; the 
distinctive features of that subordinal group being as follows. The body is 
invested in a segmented bony dermal skeleton, and the bones of the gill-cover are 
reduced to a single plate. The gill-openings are small, and the gills themselves 
consist of small, rounded tufts springing from the gill-arches; while the 
muscular system is characterised by its very slight development. I he simple air- 
bladder, when present, resembles that of the spiny-finned group in being unpro¬ 
vided with a duct communicating with the pharynx; and the prolonged muzzle 
terminates in a small toothless mouth, in which the bones are arranged as in the 
group last named. In the family under consideration the gill-openings are wide; 
the rays of the first of the two dorsal fins are not articulated; and the whole of the 
other fins are well developed. The mailed tube-mouths take their title from the great 
elongation of the tube-like muzzle; the compressed body having a very short tail, 
and, like the head, being covered with a thin skin, beneath which are the large 
bony plates, marked with a radiate pattern. The soft dorsal and anal fins arise 
from boss-like elevations of the hinder part of the body; the pelvic fins, which are 
placed close together in the same vertical line as the tall first dorsal, and have seven 
rays, are separate from one another in the males, but in the opposite sex have their 
inner edges joined to the skin of the chest so as to form a pouch for the leception 
of the eggs. The air-bladder is wanting. A female of the blue-finned species (S. 
