no UNIVERSITY OF COLORADO STUDIES 



Genus BOLEOSOMA DeKay 

 The Tessellated Darters 



Boleosoma DeKay, New York Fauna, "Fishes," p. 20, 1842. 



Much like Etheostoma; premaxillaries protractile; breeding males not so 

 brightly colored as in Etheostoma; represented in Colorado by but a single species. 



Boleosoma nigrum (Rafinesque) 

 Johnny Darter 



Etheostoma nigrum Rafinesque, Ichthyologia Ohiensis, p. 37, 1820 (Green River, Kentucky); 

 Jordan, Bull. U.S. Fish Com., Vol. IX, p. 8, i88g (Denver). 



Boleosoma nigrum (Rafinesque)— Juday, Univ. Colo. Studies, Vol. II, p. 113, 1903 (Boulder; 

 Longmont); Juday, Bull. U.S. Fish Com. for 1904, p. 227, 1905 (Boulder; Longmont). 



The Johnny Darter is a very widely distributed species ranging over the whole 

 of northern and central United States east of the Rocky Mountains. As might 

 be expected from its range and the variation of closely related species, several 

 subspecies of B. nigrum have been recognized. All of the Colorado specimens 

 examined in the present study differ from the typical B. nigrum in having smaller 

 eyes and a greater number of bands crossing the soft dorsal and the caudal fins. 

 This difference in the size of the eye places the Colorado specimens in the sub- 

 species B. nigrum mesaeum (Cope) as redescribed by Jordan and Evermann,' in 

 which the diameter of the eye is 5 in the length of the head. This subspecies was 

 founded by Cope on a single specimen collected from the Platte River, Fort 

 Kearney, Nebraska. The type unique was exceptional in having a ventral fin 

 formula of I, 4, a count verified by Jordan and Evermann (I.e.). All of the 

 Colorado specimens counted had a ventral fin formula of I, 5, and since this is the 

 t)^ical formula for all Etheostominae, Cope's specimen may have been abnormal 

 in that respect. In other characters the Colorado specimens of B. nigrum agree 

 fairly well with Cope's B. mesaeum, although from the appended table (VII) it 

 may be seen that a variation exists from the B. mesaeum type to the typical B. 

 nigrum. The reduction in the diameter of the eye, on the other hand, may be 

 merely a character of western specimens, since individuals of this species have 

 been described from Big Stone Lake, Minnesota, by Jordan and Evermann,^ with 

 an eye diameter of 4 to 4 . 5 in the head. 



Concerning the number of bands of spots crossing the soft dorsal and caudal 

 fins no data are given for B. nigrum mesaeum (Cope) by Jordan and Evermann, 

 so the relation of that species to the Colorado specimens cannot be discussed as 

 regards this character. The Colorado specimens have 5 or 6 rows of bars crossing 

 the soft dorsal and 6 to 8 rows crossing the caudal. A typical B. nigrum from 

 Illinois as figured by Forbes^ has four rows of bars on the soft dorsal and four 

 crossing the caudal fin. 



■ Bull. 47, U.S. Nat. Mus., p. 1059, 1896. » Ibid., p. 1056. 



J Forbes and Richardson, Ichthyology of Illinois, pi., p. 296, 1909. 



