DISCUSSION OF SPECIES AND THEIR DISTRIBUTION. 315 



II. Caudal not fully diflfereiitiateil, and often confluent. 



A. Ventrals inserted on isthmus, not far fnun liuniei-al sympliysis Bythitix.E 



1. I'eotorals simple. Ej'es present. 



a. Liiteral line present posteriorly, but broken in middle. 



i. Palatines deutigeron.s. Ventrals a. pair of lilaments, each of two closely united rays. 



Hythites 

 ii. Palatines toothless. Ventrals a |iair of simph^ rays (IitAMAioxus 



b. Lateral line obsolete posteriorly. 



i. Ventrals a pair of simple rays. 



* Lateral line distinct on front of body. 



t Palatines with teeth. Preoper<aiIum unarmed. 



A. Head scaly (except snout). Lateral line indistinct. 



1. Operculum with a single spine. Veut median C.-vi.ktvx 



B. Head u.aked. Lateral line on trunk only. 



• 1. Operculum without a spine. Vent postmediaii SAtcocAsTKii 



2. Oiiercnlum with twospiiu'.s. Ventpremedian .... Diim.acan tiioimma 

 tt Palatines with teeth. Preoperculum .stronj^ly armed. 



A. Head partially naked. Lateral line obsideti^ jiostcrioily. 



1. Operculum with one spine, preoperculum with 3—4 Dicko.mita 



** Lateral line obsolescent, almost or ([uite invisibh'. 

 t A feeble spine on the operculum. 



A. Head smooth. Ej'es small Bas.sozetus 



B. Head crested. Eyes large (jIlyptopiiidiim 



tt Acute spines on head-bones and opercles. 



A. A long, tapering tail. No i)yloric caM'a Derjiatihu's 



ii. Ventrals a. pair of hi lid rays. 



* Caudal rays exserted, but coulliient with those of aual and ca\ulal. 



t Head seal}'. 



A. Preoperculum with small spines at its angle. 



1. Operculum witli one s]iine Neobythites 



B. Preoperculum unarmed. 



1. Two spines on operculum. Ventrals close togi'lhcr-liKNTllocoMETES 



2. One strong spine on operculum. Veutrals far apart liA-ssonrGAS 



C. Preoperculnm with crenulated limb. 



1. Ventrals feelde, close together Alcockia 



tt Head naked. 



A. Lateral line not distinguishable. 



1. Several strong spines on head Cei.ema 



B. Lateral lino represented by a few large scales near shoulders. 



1. Head smooth. Tail very attenuate M(EitiA 



** Caudiil not confluent with vertical tins, but without distinct peduncle. 

 t Teeth on .jaws, vomer and |)alatines in villiform bauds. 

 A. Preoperculum unaruK^d. Head scaled. 



1. A flat opercular spine. 



a. Snout much produced and dilated. Lateral lim> very indistinct 

 (or absent*) Ba n atiiik ii)EMU.s 



2. Operculum with a bmiy ridge above, eudiug io a. blunt point. 



». Snout not produced, broad, rounded, llattciued at tip. Lateral 

 line obsolete posteriorly I'YCNOcnAsrEDUii 



3. Operculum a triangular flap, unarmed. 



0. Lower pectoral rays prolonged, the lowest filamentous. 



Nematonu.s 



c. Lateral line represeiited by three rows of jiores, dorsal, lateral, anil ventral. 



i. Head spinigerous. 



* Ventrals each of two distinct r.ays. Opercular spine moderate, straight. Porooadus 

 ** Ventrals each of two united rays. Opercular spine strong, curved I'E.Norus 



2. Pectorals simple. Eyes ab.seut or rudimentary. 



a. Body scaly. Ej-es absent. 



i. Ventr.als bilid fihuucuts. Teeth on jaws, vomer, and ])alatines TAUitEnopiiiniUM 



3. Pectorals with lower rays differentiated. 



a. Preoperculum armed with three spines, operculum with one. Lateral line obsolete pos- 

 teriorly. 



i. Ventrals simple, not close to.gethcr PxEROiDONrs 



ii. Ventrals bifid, approximate Dickolenk 



