326 PROCEEDINGS OF THE NATIONAL MUSEUM 



VOL. 83 



the bewildering variation in this regard throughout the entire family, 

 lessens the apparent evolutionary significance of changes in these 

 structures. Stlengis osensis, with its three bands of scales, approxi- 

 mates most closely the hypothetical, completely scaled, ancestral 

 type. The dift'erences that have occurred in the squamation of the 

 other two species have been loss variations of a type that may occur 

 readily and are of comparatively minor importance. Indeed, in the 

 course of extensive studies on the Cottidae, I have found several 

 instances where such loss variations result in striking reductions of 

 scaled areas with the increase in age of the individual. Ortlionopias 

 triads Starks and Mann and Clinocottus analis (Girard) present 

 excellent examples. 



In spite of the marked differences in squamation, the many simi- 

 larities of the three species point to their rather close relationship 

 and indicate that they form a circumscribed evolutionary line com- 

 parable in all respects to such genera as Icelus, Alyoxocephalus , and 

 Gymnocanthus. It seems advisable, therefore, to group these three 

 fishes together in the single genus Stlengis. 



Genus STLENGIS Jordan and Starks 



Stlengis Jordan and Starks, Proc. U. S. Nat. Mus., vol. 27, p. 236, 1904. 

 Schmidtia Jordan and Starks, ibid., p. 237. 

 Schmidtina Jordan and Starks, ibid., p. 961. 



Genotype. — Stlengis osensis Jordan and Starks. 



Diagnosis. — Dorsal and ventral body profiles forming almost 

 straight lines from anterior end of first dorsal (deepest point of body) 

 to caudal peduncle but bulging slightly under each of the median fins. 



Head markedly depressed, its width at base of upper preopercular 

 spines much greater than depth at same point. Jaws about equal; 

 maxillary extending to or shghtly beyond middle of pupil, its pos- 

 terior width exceeding that of narrow suborbitals. Anterior nostrils 

 in short tubes; posterior nostrils with borders little if any elevated, 

 difficult to distinguish from mucous pores. Orbit large, its diameter 

 greater than length of snout. Interorbital space flat or shghtly 

 convex; top of head gently concave, with a pair of low, rounded, 

 parieto-extrascapular elevations at the posterior border of the shallow 

 depression. Nasal spines sharp, shghtly curved, their length equal 

 to a little more than 0.5 posterior width of maxillary. Preopercle 

 armed with 4 spines, the upper one long, extending to or very slightly 

 beyond subopercular margin, with a simple or bifid tip and 3 to 5 

 recurved barbs along its upper margin; lower preopercular spines 

 simple, about as long as barbs of antlerlike spine; the upper one of 

 these simple spines directed backward, the middle one backward 

 and downward, the lower one downward and forward. A minute 

 spinous point at lower angle of subopercle and another at posterior 



