6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 56 



a curioush^ Ainia-\ike sculpture, composed almost altogether of ele- 

 ments representing the circuli, but consisting of coarse longitudinal 

 striae or strands, which are, however, continuous with the usual 

 extrcmel}^ fine and regular circuli of the concealed portion of the 

 scales, the latter having about three strong basal radii and one on 

 each side. 



Alcstes nurse. Very similar in appearance to A. harcmose, but deeper-bodied. 

 The strong apical circuli are mainly longitudinal, meeting at an acute 

 angle in the middle line. The apical radii often have transverse 

 branches, more or less in the manner of a spreading tree; usually 

 there is a single apical radius, with branches leaving at right angles, 

 but in the dorsal and ventral regions there are more. 



Alcstes baremose. The sculpture, on close comparison, is really very distinct 

 from that of ^. nurse. The apical circuli, instead of forming regular 

 grooves, are evanescent, reduced to a fine rugosity ; the apical field is 

 sparsely punctate ; the one to three apical radii are usually incom- 

 plete, and show no lateral branches. The ventral and dorsal scales 

 show many thin, weak, parallel apical radii. 



Alestes opisthotcsnia Boulenger, from Efulen, Cameroon (G. L. Bates) has 

 rather large (about 8 mm. long and 10 broad) white scales, resemb- 

 ling those of the aMnis group ; with four basal radii, discal polygonal 

 areas, and coarse apical circuli. The interesting feature of the scale 

 is, however, that it is subctenoid, with small but very evident apical 

 denticulations. The teeth are broader than long, and indicate the 

 beginning of such structures as are found, much better developed 

 and much reduced in number, in Citharidium ansorgii. The ctenoid 

 scales of Distichadus, Xenocharax, etc., are entirely different. There 

 are slight indications of apical denticulation in some other Alcstes^ 

 as A. rhodopleura and A. imberi. 



MlCRALESTES 



The scales of this genus cannot be distinguished from those of Alestes; that 

 is to say, there is no generic difference, though specific distinctions may be 

 found to separate any particular species of Micralcstes from any particular 

 Alestes. The scales are always conspicuously broader than long. 



Group A. Apical circuli strong, coarse, and complete, those of the two sides 



meeting at an obtuse angle. 

 Micralestes Iwlargyreiis Giinther. Boma (Dclhc:). 



Scale 3.5 mm. long, 5.33 broad ; si.x: radii, all strong and complete, one 



apical, one basal, and two on each side: no polygonal areas. In 



Alcstes it comes near to A. longipinnis. but it is a shorter scale, with 



much better developed apical sculpture. 



Group B. Apical sculpture feeble, the circuli ill-defined, although the basal 

 circuli are very distinct. 



Micralcstes altus Boulenger. Lindi, Congo (Brussels Museum). 



Scale about 5 mm. long and 7 broad ; basal circuli much denser than 

 lateral; three basal radii, one apical, one or two on each side; no 

 polygonal areas. (These characters will vary; I doubt whether there 

 is any constant difference in the radii lietwcen llie si)ecies of Micra- 

 lcstes.) 



