1028 Bulletin 47, United States Natio?ial Museum. 



number; a black caudal spot; dorsal and caudal mottled. Lakes of 

 northern Indiana, Michigan, Wisconsin and northward to Lake Superior ; 

 the common form in the Great Lakes. The typical zdwa is well distin- 

 guished from cajfi'odes, but specimens variously intermediate have been 

 obtained in Illinois by Dr. Forbes and in the Potomac by Dr. Bean. 

 (zebra, a striped wild horse ; from the color. ) 



Pileoma zebra, Agassiz, Lake Superior, 308, 1850, Lake Superior: Vaillant, Recherclies, 48, 



1873, with plates. 

 Percina vianiton, Jordan, I'roc. Ac. Nat. Sci. Phila., 1877, o.i, Lake Manitou, Rochester, 



Indiana. 

 Percina caprodes manUmi, Jordan Jt Gilbert, Syuopsis, 500, 1883. 



466. HADROPTERUS, Agassiz. 

 (Black-sided Darters.) 



Hadroptfrvs, Agassiz, Aiiier. Jouni. Sci. and Arts*, 1854, 305, (nujrofanclalits). 



Elheosloma,* Agassiz. Anier. Journ. Sci. and Arts, 1854, 305, ( •'bleituioides'' (not of Rafinesqt'E 



= aspro), 

 Alvordius, Girarp, Proc. Ac. Nat. Sci. Pliila., 1^59, 68, (^maculalns). 



Plesioperca, Vaillant, Reclierches sur Poissous des Eaux Donees, Etlieostomatina, {aticeps). 

 Ericosmu, Jordan & Copei.and, Bull, x, U. S. Nat. Mus., 8, 1877, (evides). 

 Serraria, Gilbert, Proc. U. S. Nat. Mus., 1884, 205, {acienix). 



Body rather elongate, compressed or not. Mouth rather wide, terminal, 

 the lower jaw Included, the snout above not protruding beyond the pre- 

 maxillaries, which are not protractile. Teeth on vomer and usually on 

 palatines, also. Gill membranes separate or more or less connected. 

 Scales small, ctenoid, covering the body. Belly with a median series of 

 more or less enlarged spinous plates or ctenoid scales, which in most spe- 

 cies fall off at intervals, leaving a naked strip; in some species persistent 

 and but slightly enlarged ; sides of head scaly or not ; lateral line com- 

 plete or nearly so. Fins large, the soft dorsal smaller than the spinous or 

 the anal ; anal spines 2 (one of them very rarely obsolete) ; dorsal spines 

 10 to 15. Ventral t fins more or less widely separated, especially in species 



* The name Elheosioma can not be used for this group as none of its species was known to 

 Rafinesque, who based the genus Etheostoma on caprodes, blennioides, and flabellare. 



t Tiiis character of the separation of the ventrals " by an interspace equal to the width of their 

 base" was tirst introduced as a generic feature by Dr. Boulenger (Cat. Teleosteau Fishes, i, 45). 

 It is used by him to separate Percina (= Percina + Alvordius) from Elheosloma (= Etiieoslonui + Hypo- 

 hoiinis + Serraria + Hadropterus proper + Pwcilichlhya + Boleichtlnjs -j- Alvarius, etc.), in which the 

 ventrals are said to be "separated by an interspace considerably less than the width of their 

 base." In like manner B'ilensoma (including Colloyaster) is separated from Ulocentra and Diplesum, 

 the former having the ventrals widely separated. In Ammocri/pta the interspace is equal to the 

 width of tlie base. To ascertain the value of ti,jg character we liave, with the assistance of Dr. 

 Meek, examined most of the si)ecies of Elheoslowiiuc. We fiud that in the extreme forms, Percina, 

 Crijslallaria, Buleosoma. Ammocrijpta on the one hand, the ventrals are widely separated, as stated 

 by Dr. Boulenger. On the other hand, in s{iecies related to Etheostoma flabellare and E. cieiuleiim, 

 they are very close together. Between these extremes, however, we find every gradation. This 

 character, like other characters, shading off by degrees, and many of thos« specie.'; described by 

 Dr. Boulenger as having tlie fins close together, would he placed by us rather with the others. 

 The comparison of the interspace with the width of the b.ase of the fin is not wliolly. satisfactory, 

 as the base of tlie fins appears broader in the males with enlarged rays and narrower in the 

 young. In general those species with the most elevated crania have the ventrals nearest 

 together, a character usually going with small anal fin and sliort first dorsal, excejit among the 

 allies of Ammocrijpta and Boleosomu, The Bpecies examined by us may be roughly placed in four 

 groups, thus: 



