FISHES OF NEW YORK ' 351 



and the fact that the male carries the eggs and protects the 

 young in a pouch behind the vent. In this egg sac the young 

 are protected till large enough to live independently, going out 

 in search of food and returning to their shelter at pleasure. 



Order acanthopteri 



Spiny-rayed Fishes 

 Suborder sadmoperoae 



Trout Perclves 

 Family percof'sidae 



Sand Roll&rs 

 Genus percopsis Agassiz 

 Body rather slender, pellucid, covered with rather thin scales; 

 dorsal fin with two slender spines or simple rays; anal with one; 

 scales roughest posteriorly; lateral line developed; preopercle 

 entire or very nearly so; vertebrae 17+17=34. Atlantic slope, 

 in cold or clear lakes and rivers. 



176 Percopsis guttatus Agassiz 



Trout Perch; Sand Roller 



Percopsis guttatus Agassiz, Lake Superior, 286, pi. I, figs. 1, 2, 1850, Lake 

 Superior; Gunther, Cat. Fish. Brit. Mus. VI, 207, 1S66; Jordan & Gil- 

 bert, Bull. 16, U. S. Nat. Mus. 322, 1883; Bean, Fislies Penna. 84, 1893; 

 EvERMANN «fe Kendall, Rept. U. S. Cominr. Fish & Fisheries for 1894, 

 599, 1896 from Thompson; Jordan «& Evermann, Bull. 47, IT. S. Nat. 

 Mus. 784, 1896, pi. CXXI, fig. 329, 1900. 



Salmoperca pellucida Thompson, Appendix Hist. Vermont, 33, 1853, Lake 

 Ohamplain. 



Percopsis hammondi Gill, Proc. Ac. Nat. Sci. Phila. 151, 1864, Kansas. 



Body rather long and moderately compressed, covered with 

 thin ctenoid scales; head scaleless and without barbels; gill 

 openings wide; opercles well developed; gill rakers short, tuber- 

 cular; skull highly caA'ernous; mouth small; the margin of the 

 upper jaw formed by the short nonprotractile intermaxillaries; 

 no supplemental maxillary bone; small villiform teeth on the 

 intermaxilliaries and mandible. The tongue is short, not free 

 at tip. Pseudobranchiae developed. Six branchiostegals. The 

 lateral line is continuous. The first dorsal over middle of body, 

 with nine to 11 developed rays; adipose fin small; the anal and 

 ventral eight rayed; caudal long, forked; pectorals narrow, 



