Page:Quarterly Journal of the Geological Society of London, vol. 32.djvu/161

Rh known and unsuspected as reptilian ones by zootomists, save through the researches of the palæontologist.

If the gap in the animal series between the Mesozoic and bimanous air-breathers had not been filled up otherwise than by reptiles, the remnant of that class which has survived and reached our times would have testified to total loss of such gains of organization as had enriched the ancestors or predecessors of modern tortoises, lizards, and crocodiles.

We now know that not one of these gains has been lost, but has been handed on and advanced through a higher type of Vertebrata, of which type we trace the dawn back to the period when Reptiles were at their best, grandest in bulk, most numerous in individuals, most varied in species, best endowed with kinds and powers of locomotion and with the instruments for obtaining and dealing with food.

Has the transference of structures from the reptilian to the mammalian type been a seeming one, delusive, due to accidental coincidence in animal species independently (thaumatogenously) created? or was the transference real, consequent on nomogeny or the incoming of species by secondary law, the mode of operation of which we have still to learn? Certain it is that the lost reptilian structures dealt with in the present paper are now manifested by quadrupeds with a higher condition of cerebral, circulatory, respiratory and tegumentary systems, the acquisition of which is not intelligible to the writer on either the Lamarckian or the Darwinian hypothesis.

Fig. 1. Nodule of Karoo clay-stone with fore part of skull, the upper canines exposed (c, c).

2. Side view of crown of right upper canine.

3. Transverse section of ditto at the dotted line c, fig. 2.

4. Portion of canine, magn. 2 diam., showing serrations of the trenchant hind border, c.

5. Upper view of fore end of mandible, showing transverse sections of the crown-base of the incisors (i 1, 2, 3, 4) and canines (c′), with the crowns of the upper canines (c, c).

6. Front (thenal) view of left humerus, half natural size.

7. Back (anconal) view of left humerus, half nat. size.

8. Proximal end, abraded, of left humerus, half nat. size.

9. Distal end, less abraded, of left humerus, half nat. size.

10. Front (thenal) view of left humerus of Uromastix spinipes, nat. size.

11. Back (anconal) view of left humerus of Uromastix spinipes, nat. size.

In the figures of the humerus, a, "head;" b, ectotuberosity, here the beginning of the delto-pectoral crest (b b′); c, entotuberosity, not well defined; d, olecranal depression; e, beginning of "supinator ridge," ending at e′, the ectepicondyle (the ridge is less developed in Uromastix); f, entepicondylar ridge; f′, entepicondyle ; I, ulnar condyle ; g, radial condyle ; h, bridge defining k, the entepicondylar canal (fig. 6); m, bridge defining the ectepicondylar canal (figs. 10 and 11). All the figures of the natural size, save where otherwise expressed.