Fig. 150. — Calamoichthys calabaricus. xX}. Senegambia, 
TELEOSTOMES 
recent forms may be included the fringing dor- 
sal fin, the tubular nasal opening (Fig. 149), 
and an external gill in Polypterus (Steindach- 
ner), ZG, in the late larval stages. 
Calamoichthys is unquestionably a divergent 
member of the stem of Polypterus; its form, 
becoming elongated, has acquired a general un- 
dulatory movement ; the paired fins have accord- 
ingly diminished in relative size, the ventral fins 
finally disappearing. 
Little is known of either the living or breed- 
ing habits of Crossopterygians: in these they 
might naturally be expected to resemble the — 
Ganoids. 
Fossil Crossopterygians 
A number of the fossil kindred of Polypterus 
are shown in the succeeding figures (Figs. 151- 
156 A). 
Gyroptychius and Osteolepis, Devonian genera 
(Figs. 151, 152), are certainly most nearly in 
the ancestral line of the recent forms. Like 
many sharks and fossil Dipnoans, they present 
a heterocercal tail, a single anal fin, and a pair 
of dorsals. The pectoral fin of Osteolepis is 
becoming a typical archipterygium. : 
Holoptychius, another Devonian form (Fig. — 
153), approaches even more closely the dipnoan 
types: the scales are cycloidal; its paired fins 
are distinctly archipterygial; and the caudal 
region, reduced in length, is becoming meta- 
morphosed into the typical diphycercal form by the ten- 
dency of the second dorsal and anal fin to coalesce with 
