OBSERVATIONS ON FISH SCALES. 
I2I 
Order CLADISTIA. 
POLYPTERID^. 
The scales of Polypterus etidlicheri Heckel from the White Nile (British Museum) are entirely of a 
dense bony consistence, the exposed surfaces rhombic or diamond-shaped with an enamel-like coating. 
The scales are produced into a long concealed process, and each has a peg or tooth fitting into a hole 
or socket in the next scale. Although Polypterus belongs to a very primitive group, its scales must be 
considered highly modified; the protection they afford may perhaps explain the survival of the genus. 
It is in Coelacanthus, not in Polypterus, that we get the real clue to the affinities of the crossopterygians. 
Subclass DIPNEUSTl. Lungfishes. 
Order CTENODIPTERINI. 
CTENODONTID/E (Fossil). Comb-toothed Lung fishes. 
The large scales of Sagenodus from the Carboniferous of Mazon Creek, 111. (American Museum of 
Natural History), almost entirely agree with those of the living N eoceratodus . Aside from the irregular 
radii, forming a network in the central part of the scale, both form and structure are very near to those 
of the bowfin, Amia; and both, except for the lack of grooves in the exposed region, approach Coela- 
canthus. The one important feature in which all these agree is the large concealed area consisting of 
longitudinal fibrillse. Among the Teleostei we find this retained only in the bonefishes, Albulidae, 
Order SIRENOIDEI. Sirenoid fishes. 
CERATODONTID^. Flatheads. 
N eoceratodus forsteri, from Queensland (British Museum), has very large elongated scales with 
longitudinal beaded fibrillse and a radial system of reticulation. (Science, May 26, 1911, p. 831.) 
The radial network and the tuberculate or beaded fibrillas distinguish these scales from those of Aviia. 
LEPIDOSIRENID^E. Scaly sirenids. 
The scales of Lepidosiren and Protopterus are briefly described in Science, May 26, 1911, page 831. 
Although these fishes come from widely separated regions (South America and Africa) and rmdoubt- 
edly represent different subfamilies (Lepidosireninse and Protopterinse), their scales are almost exactly 
alike. There is a strongly developed radial network, as in the Osteoglossidae, and the surface is 
minutely tuberculate, the tubercles derived from beaded fibrillas. The scales are inclosed in the 
skin, and are circular or approximately so, not elongate as in Neoceratodus and Sagenodus. 
Subclass ACTINOPTERI. 
Superorder GANOIDEI- 
In this case I prefer to write " superorder, ” rather than “series,” as the term defines the rank of the 
category in relation to others. 
Order GINGLYMODI. 
LEPISOSTEID^. Gar pikes. 
The rhomboidal ganoid scales of the gar pikes Lepisosteus have a very close superficial resemblance 
to those of Polypterus, a case doubtless of convergence of type, due largely to the mechanical necessities 
of the situation. The scale of Lepisosteus is not so highly specialized as that of Polypterus, since it 
lacks the well-defined peg-and-socket arrangement. (For a further discussion of the scales of these 
genera, see Goodrich, Proceedings Zoological Society of London, November, 1907, p. 762-763.) 
