488 CONTRIBUTIONS TO NOETH AMERICAN ICHTHYOLOGY IV. 



latter bearing a strong external resemblance to the Etiieostomatince, and 



serving as a connecting link between them and the more typical forms. 



(Percidce j)art, Giinther, i, 58-78; genera Perca, Luciopcrca, Pileoma, Bohosoma, Ace- 

 rina, Peicariiia, Aspro, Pertichthys, and. Percilia.) 



* Anal spines one or two. 



a. EseucTobrauchiai imperfect or wanting; preopercle entire; brancloiostegals 6. {Ethe- 



osiomafince.) 

 i. Premaxillaries protractile. 

 c. Body extremely elongate, subcyliudrical, translncent, the belly at least naked; 

 lateral line complete; gill-membranes broadly united. 

 d. Anal si^ine single ; anal tin nearly as large as second dorsal. 



Ammoceypta, 252. 



dd. Anal spines two ; anal fin small Ioa, 253. 



cc. Body less elongate, opaque, chiefly scaled. 

 e. Anal spine obscure, normally single. 

 /. Lateral line complete, or wanting on a few scales only.-BoLEOSOMA, 254. 



ff. Lateral line incomplete Vaillantia, 255. 



ee. Anal spines two, the first commonly tbe longer. 



g. Gill-membranes more or less broadly united ; belly with ordinary scales. 



7(. Maxillary bone normal Ulocentra, 256. 



hh. Maxillary adnate to the preorbital Diplesium, 257. 



gg. Gill-membranes scarcely connected. 



i. Belly with enlarged caducous plates Cottogaster, 258. 



ii. Belly without enlarged caducous ijlates Imostoma, 259. 



65. Premaxillaries not protractile. 



j. Lateral line complete. 



Jc, Ventral line with a series of enlarged, spinous, caducous scales 

 or (if these are fallen) a naked strip. 

 I. Mouth small, inferior, beneath a pig-like snout . . Percina, 260. 

 U. Mouth larger, the snout not projecting beyond it. 



AlvordiTjS, 261. 

 ]ck. Ventral line without caducous scales. 

 m. Gill-membranes scarcely connected. 



n. Anal fin larger than second dorsal Hadropterus, 262. 

 nn. Aual fin smaller than second dorsal . .Nothonotus, 263. 

 mm. Gill-membranes broadly connected .. .Naxostoma, 264. 

 jj. Lateral line present, incomplete. 



0. GiU-membranes broadly united Etheostoma, 265. 



00. Gill- membranes separate or nearly so. 



Pcecilichthys, 266. 



jjj. Lateral line obsolete Microperca, 267. 



aa. Pseudobranchiaj well developed ; jjreopercle serrate ; brauchiostegals7. (i ercina'.) 



J). Canine teeth none ; body oblong Perca, 238. 



jjp. Canine teeth in jaws and palatines; body elongate. 



SllZOSTEDlUM, 269. 

 252.— AMMOCKYPTA Jordan. 



Sand Darters. 



{* Phurolcpis Agas3iz; not Plcurolepis Egerton, a genus of extinct Ganoids.) 



(Jordan, Bull. U. S. Nat. Mus. x, 6, 1877: type Amniocri/pia bean? Jordan.) 



Body slender and elongate, sub-cylindrical ; pellucid in life. Head 

 * Agassiz, Bull. Mus. Comp. Zool. i, 5, 1863: type Etheostoma pellacidum Bainl MSS. 



