394 DR TRAQUAIR ON THE STRUCTURE AND AFFINITIES 
distinctions. Dr Lirxen* has already proposed to unite those genera having 
rhombic scales with the Sauwrodipterini, under the name of Rhombodipterini, an 
arrangement in which I am much inclined to concur—the remainder with 
rounded imbricating scales being designated Cyclodipterim. But among these 
Cyclodipterini there occur fishes with two somewhat different types of pectoral 
fin—those in which that member is very acutely lobate, like that of Dipterus, 
or of the recent Ceratodus (Holoptychius, Glyptolepis), and those in which it is 
only subacutely so, the lobe terminating considerably before the end of the fin, 
which consists of more elongated rays, especially in the central part (Z7risti- 
chopterus, Rhizodus, Rhizodopsis). Following Dr GUNTHER in associating the 
Ctenododipterini (Dipterus, Ctenodus) with the Dipnoi, I would therefore, pro- 
visionally at least, propose the following modification in the arrangement of 
the remaining Crossopterygidee :— 
I. Caudal diphycercal, but with shortened body-axis. Dorsal fin multifid, pectorals obtusely lobate, 
scales rhomboidal. 
Fam. 1.—Polypteridee (Polypterus, Calamoichthys). 
II. Caudal with elongated attenuated body-axis, heterocercal or diphycercal. 
A. Pectorals obtusely lobate, tail diphycercal, dorsal fins two, scales cycloidal, air bladder 
ossified. : 
Fam, 2—Ceelacanthide (Celacanthus, Macropoma, Holophagus). 
B. Pectorals subacutely lobate, dorsal fins two, tail heterocercal or diphycereal. 
a Scales rhomboidal. 
Fam. 3.—Rhombodipteride. 
* Scales sculptured, 
Sub-fam.—Glyptolemini (Glyptolemus, Glyptopomus). 
** Scales smooth. 
Sub-fam.—Saurodipterini (Osteolepis, Diplopterus, Megalichthys). 
B Scales cycloidal, sculptured. 
Fam. 4.—Cyclodipteride (Tristichopterus, Gyroptychius (2), Rhizodus, Rhizo- 
dopsis, Strepsodus, Archichthys (?) ). 
C. Pectorals acutely lobate, scales cycloidal. 
a Dorsal fins two, ventrals subacutely lobate, scales thick, sculptured. 
Fam. 5.—Holoptychiide (Holoptychius, Glyptolepis, Don odus (2), Cricodus (?) ). 
B Dorsal fin elongated, continuous with the upper part of the au ventral fins” 
acutely lobate; acales thin. 
Fam. 6. = Phancroplennides (Phaneropleuron, Uronemus). 
I have placed the genus Gyroptychius, M‘Coy, in the family of Cyclo- 
dipteride, next to Tristichopterus, with a mark of interrogation, because, 
according to PANDER’s elaborate description,t it seems to approach the subject 
of the present memoir nearer than does any other genus hitherto described, in 
the sculpturing of the head plates, and of the scales, which, according to that 
author, “sind elliptisch und bedecken sich dachziegelartig.” The fulcration of 
the fins, the rhomboidal diphycercal form of the caudal, and the greater relative — 
* Ueber die Begrenzung und EHintheilung der Ganoiden; Paleontographica, Bd. xxii, Erste 
Lieferung, 1873, p. 47. 
t+ Op. cit. pp. 55-61. 

