Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/673

Rh deutlich erkennbaren Wirbelsäule, an seiner, wenn auch in verminderter Höhe sich fast bis zur Schwanzflosse fortziehenden Afterflosse, wesshalb man ihm auch die Benennung Afterflossenfisch geben kann, und an der, der Afterflosse fast gerade gegenüberstehenden Rückenflosse." Again he remarks:—"Die Afterflosse beginnt bei zwei Drittheil Länge des Bauches, dehnt sich anfangs stark in die Höhe aus, wird dann aber schnell wieder niedrig, und setzt sich nachher mit allmählig verminderter Höhe bis in die Nähe der untern Schwanzflosse fort. Die Rückenflosse steht der Afterflosse ziemlich gerade gegenüber, doch noch weiter nach vorn gerückt, so dass etwa ihre Mitte dem Anfange der Afterflosse sich gegenüber befindet, sie steigt auch anfangs schnell und hoch empor und endigt nach hinten durch eine sichel- oder halbmondförmige Ausbüchtung ".

The definition of Pyyopterus given by McCoy is as follows:—

"Body large, elongate ovate; fins very large, with fulcral scales, anal fin of moderate depth and very long, dorsal of moderate length, nearly opposite or a little in front of the anal fin; ventrals small, slightly in front of the middle of the body; pectorals moderately small, falcate caudal very large, deeply notched; upper jaw a little longer than the lower; endoskeleton strong, vertebræ usually wider than long; scales proportionally rather small, rhomboidal, smooth, and minutely punctured or diagonally striated, extending over the pedicles of the fins, and particularly over the thick upper lobe of the tail to the extremity, having a moderately wide articular margin, sometimes prolonged at the upper angle, and having a medial internal articular ridge which forms a prolongation from the middle of the upper margin".

What, therefore, the salient generic characters of Pygopterus are, is perfectly clear from the foregoing extracts, which all refer to the Permian species P. Humboldtii and P. mandibularis; for even Agassiz, though he enumerated several other species from the Carboniferous formation, made only the briefest possible reference to their distinctive characters, deferring that description to a future opportunity, which, unfortunately for fossil ichthyology, never arrived. These two species, which, indeed, resemble each other exceedingly closely, must therefore be taken as typical of the genus. It now remains for us to inquire whether the others named by Agassiz sufficiently agree with them in structure to warrant their retention under the same generic title.

The species of "Pyyopterus" enumerated by Agassiz, in his general list of Ganoids, are the following:—

1. P. Bonnardi, Muse, near Autun.

2. P. Bucklandi, Burdiehouse.

3. P. lucius, Saarbriickcn.

4. P. Jamesoni, Burdiehouse.

5. P. Greenockii, Newhaven.

G. P. Humboldtii.

7. P. mandibularis.

8. P. sculptus.