THE MAILED TUBE MOUTHS 2795 



THE MAILED TUBE MOUTHS Family SOLENOSTOMATID^E 



A few small fishes from the Indian Ocean constituting the genus Solenostoma 

 are the sole representatives of the first family of the suborder L,ophobranchii; the 

 distinctive features of that subordinal group being as follows: The body is in- 

 vested 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 characterized by its very slight development. The simple air bladder, 

 when present, resembles that of the spiny-finned group in being unprovided 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 



BLUE-FINNED TUBE MOUTH. 

 (Natural size.) 



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 reception of the 

 eggs. The air bladder is wanting. A female of the blue-finned species (S. cyano- 

 pterum) is shown in the accompanying illustration; the range of this form ex- 

 tending from the coast of Zanzibar to China and Ceram. The female takes the 

 whole charge, not only of the exceedingly-minute eggs, but likewise of the 

 newly-hatched fry. Like the members of the next family these fishes generally 

 swim in a more or less nearly vertical position, the dorsal fin exerting the chief 

 propelling power. The family is represented by an extinct genus from the Ital- 

 ian Eocene. 



