120 Bulletin 4.7, United States National Museum. 



b. Anal fin twice as long as high, with 22 rays ; fontanelle with an indistinct groove; 



occipital process twice as long as broad ; sides freckled. LENTIGINOSUS, 163. 



bb. Anal fin higher than long, with about 15 rays ; fontanelle continued as a deep groove 



to base of occipital process, which is 3 times as long as broad ; sides with a broad 



pale band. PERUVIANTJS, 164. 



aa. Occipital process .and bones of head exposed or covered with very thin skin ; bones on top 



of head and occipital process granular. 



c. Palatine patches of teeth with a backward projecting angle on the inner margin (this 



often obsolete in the young in Selenaspis); vomerine bands contiguous or confluent. 

 General color brown, with bronze reflections. 



d. Dorsal plate saddle-shaped, enlarged ; its length on the median line more than J v 

 that of head ; teeth on the palate villiform or bluntly conical ; vomerine bands 

 of teeth united. 



SCIADEICHTHYS, (Sciades, a related genus, from a-xid, shade ; ixflvs, fisb ) : (genus 70.) 

 e. Posterior nasal openings not connected by a membrane. Species 165-172. 



/. Dorsal plate longer than broad, pointed in front, entering the short, emargi- 

 nate occipital process; fontanelle large, ending acutely at a point 

 nearer base of dorsal than tip of snout ; eye moderate, F>% or less in 

 interorbital space ; maxillary barbels not reaching beyond base of pec- 

 torals ; no pterygoid teeth ; head 3% in length. TROSCHELI, 165. 



SELENASPIS, (o-eArjvjj, the moon ; ao-jn's, shield:) (genus 71.) Species 173 to 176. 

 ee. Posterior nasal openings connected by membrane (young with the dorsal 

 plate reduced and no backward prolongation to palatine patch of teeth). 

 Dorsal shield much broader than long, its anterior margin truncate. 

 g. Occipital process very short, truncate behind, % wider at base than at 

 tip, its length less than % its greatest width ; gill rakers 7 + 15; 

 fontanelle short, ending obtusely at a point much nearer tip of snout 

 than front of dorsal ; head 3% in length. DOWI, 174. 



dd. Dorsal plate crescent-shaped, not enlarged, its length on the median line much 



less than ^ head. 

 NETUMA, (Netuma Jceleii, a name used at Pondicherry for Netuma netuma) : (genus 72.) 



Species 177 to 185. 

 h. Occipital process widest at its base. 



i. Fontanelle obtuse, not produced backward as a groove ; interorbital region 

 granular ; barbels short ; caudal not % head ; posterior nostrils not 

 connected by membrane ; head very large, 3% in length. 



KESSLERI, 180. 



it. Fontanelle continued backward as a groove (in one species nearly obso- 

 lete), and the top of head not granular. 



j. Interorbital region and shields of head finely granular ; no axillary 

 pore ; maxillary barbels long, reaching middle of pectorals ; cau- 

 dal more than % head, which is 4 in length. 



INSCTJLPTUS, 181. 



jj. Interorbital region flat and smooth or with smooth ridges, a triangu- 

 lar smooth area extending backward from it. 

 fc. Vomerine patches of teeth united, except in young. 



I. Groove of fontanelle almost obsolete, not reaching occipital 

 process, which is about as broad at base as long, with con- 

 cave margins ; caudal a little shorter than head, which is 

 3 in length ; shields of head coarsely granular. 



PLANICEPS, 182. 



K. Groove of fontanelle well defined, reaching occipital process, 



which is longer than broad at ba?e and with straight edges; 



barbels short, compressed at base ; head long 3f in length, 



. its shields finely granular ; paired fins often black at base. 



PLATYPOGON, 183. 



Kk. Vomerine patches of teeth separate on the median line. 



