GENUS MINYTREMA. 137 



raiely 8 or 10. Anal fin high and short, often more or less emarginate 

 in males. Caudal fin moderately forked, the lobes about equal. 



Air-bladder with two chambers. 



Males in spring with the head covered with many small tubercles. 



But one species of this genus seems to be kuow^n. It is widely dis- 

 tributed in the waters of the Western and Southern States. 



This genus has been recently separated from Erimyzon, on account of 

 the peculiarities of the lateral line. The form of the body, the form of 

 the mouth, and the character of the squamation differ considerably in the 

 two genera. , 



Generic Characterizations. 



MiNYTREMA Jordan, 1878. — "Young specimeus of this epecies (melanojjs) have no 

 trace of a lateral line, as iu Erimyzov. Older ones (6 to 8 inches) show a deepening of 

 the furrows along the median series of scales. Adults of 12 to 18 inches show a series 

 of completely developed tubes, which, however, are wanting on some of the scales, espe- 

 cially behind. As Erimyzon never shows any traces of the tubes of the lateral line, these 

 peculiarities may be held to indicate generic distinction, and the name Minijtrema is 

 here proposed for E. melanops." — (Jordax, Man. Vert. ed. 2d, 318, 1878.) 



AJSTALYSIS OF SPECIES OP >nNYTKEMA. 



* Body oblong, little compressed; the young nearly terete ; the adults deeper-bodied; 

 the dorsal region not elevated : depth about 4 in length, varying from about 3 in 

 adults to 4i in the young : head not very large, 4-J in length of body (4J to 4^), 

 not specially depressed: mucous pores rather stiong: eye small, 5 to (j iu head: 

 mouth quite inferior, horizontal, rather small : scales large, firm, regularly and 

 smoothly imbricated, in 46 (44-47) longitudinal series and 13 (12 to 14) transverse 

 series, the scales not crowded forwards : fin-rays usually, dorsal 12,* anal 7, ven- 

 trals 9. 



Coloration dusky above, with usually a black blotch behind the dorsal fin : each 

 scale along the sides with a small, more or less distinct blackish spot at iis base, 

 these spots forming interrupted longitudinal lines along the rows of scales. 

 These lines are usually very distinct, * specially in the adult, but young specimens 

 often show them faintly: sides and belly silvery, with a coppery lustre: sexual 

 peculiarities moderately marked; very old males with the head covered with small 

 tubercles in spring : no great changes with age, either in form or coloration : size 

 large ; maximum length about 18 inches melanops, 20. 



* As in all cases in the present paper, the numler of developed rays is here understood, 

 the one, two, or three rudimentary rays not being counted, and the last or double ray 

 of the dorsal and anal being counted as one. 



