SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 56 



suggests the probability that the Teleosts with very fine and dense 

 circuli {e. g., the majority of the Old World Cyprinids) are so far 

 more primitive than those in which the circuli are fewer {e. g., the 

 New World Cyprinids, but not the Catostomids), as had already 

 been assumed on other grounds. 



The radii, according to this theory, are of secondary origin. In 

 some cases they may lose their radial arrangement, and more or less 

 simulate circuli. This is seen in Alosa sapidissima Wilson (fig. i), 

 the circuli of which are extremely fine and delicate, while the radii 

 of the basal field actually take the form of widely spaced transverse, 



almost concentric lines. In some of the 

 scales (the larger and broader ones) this 

 development is so complete as to conceal 

 its origin, but in other scales on the same 

 fish the various transitional states can be 

 perceived. 



On the other hand the circuli may also 

 become transverse, losing the appearance 

 of concentric lines. This is excellently 

 sho^\•^ in Scomber chrysozonus, from 

 Massauah (pi. i, fig. i) ; that the lines 

 really are circuli is proved by the scale of 

 Scomber pnewnatophoriis (Table Bay, 

 Cape of Good Hope), (pi. i, fig. 2), in 

 which they are still obviously circuli. 



The African Characinidae have scales of two main types, which 

 seem to be wholly distinct. The first, including the Hydrocyoninse 

 and Citharininae, may be called the Cyprinoid type, showing a dis- 

 tinct — often strong — resemblance to the scales of the Cyprinidse. In 

 this type the nuclear area is central, or nearly so, and the scales are 

 usually cycloid, rarely ctenoid, and when so not at all like the ctenoid 

 scales of the other group. 



The second or ctenoid group proper includes the Ichthyoborinae 

 and Distichodontinse, which cannot be separated on the squamation. 

 In this series the apical teeth are very regular and numerous, united 

 laterally, and the nuclear area is almost at the apex, the base being 

 thrown more or less into folds. This basal folding appears to lead 

 to the very distinctive system of basal radii found in the Acan- 

 thopterygian and allied fishes; e. g., in Tilapia nilotica (Cichlidse), 

 (pi. I, fig. 3), Apomotis cyanellus (Centrarchidse), Cyprinodon 

 fasciatus (Cyprinodontidae), and Anabas mimii (Anabantidge). 



Fig. I. Alosa sapidissima 

 Wilson 



Drawn by Miss E- V. Moore 



