RECENT CROSSOPTER YGIAN 149 
their isolated position, these recent forms become of ex- 
treme interest to the morphologist, and from the side of 
their development, when this comes to be studied, they are 
expected to throw the greatest light on the relations of the 
primitive Teleostome to the sharks and Dipnoans, on the 
one hand, and to the Ganoids on the other. 
Polypterus * presents the exoskeletal characters of the 
ancient Crossopterygians, and the typical conditions of 
their lobate pectoral fins; the dermal plates of its head 
region are tuberculate as in Dipnoans, but, unlike 
these, their arrangement, as in all Teleostomes, is dis- 
Fig. 149.— Polypterus lapradei, (After STEINDACHNER.) Head region of 
well-grown larva showing external gill, ZG. 
tinctly paired, ze. “ethmoids,” frontals, parietals, occipi- 
tals (Fig. 148 A), including a pair of gular plates in the 
throat region, 8.| Among the structures peculiar to the 
* Polypterus occurs in the Nile, but is rarely taken below the Cataract. It 
was noted, however, from near Cairo in the Description d’Egvpte, and a spec- 
imen in the possession of Professor Innes of the College of Medicine, Cairo, was 
taken near Bofilak a few years ago. It is known by the Arabs near Assuan, 
and is here occasionally taken in the fykes at the beginning of the flooding- 
season. The remarkable series of Polypterus in the Vienna collection was 
collected in the White Nile, although some of these specimens, Dr. Stein- 
dachner has stated personally to the writer, were taken in Middle Egypt. It 
_ seems evident to the writer, from the results of his collecting-trip from Cairo 
to Assuan, April and May, 1892, that abundant material of Polypterus is not 
readily secured below the Second Cataract. Until, therefore, the interior of 
Egypt is made more accessible to foreigners, developmental stages can hardly 
be hoped for. 
t As in some of the fossil lung-fishes. 
