652 SCIENCE PROGRESS 



portion of the subject must be extremely.brief, the first papers for 

 notice are connected with the structure and origin of the primi- 

 tive types of fin-structure, and the evolution therefrom of the 

 tetrapod limbs of the higher vertebrates. In the first of these 

 Mr. Watson (Anat. Anzeiger, vol. xliv. pp. 24 et seq.) ex- 

 presses the opinion that the limbs of the Tetrapoda have 

 been evolved from a reduced archipterygium such as occurs 

 in the crossopterygian genus Eusthcnopteron. Dr. Broom {Bull. 

 Amer. Mus. Nat. Hist. vol. xxxii. pp. 459-64), on the other 

 hand, favours the view that the chiropterygium, as found in 

 Sauripteris, is nearer the type from which the tetrapod limb was 

 developed ; this form of fin being of particular interest from the 

 fact that it was used partly for progression on land. It is, how- 

 ever, of a too specialised type to have given rise to the tetrapod 

 limb, and the author accordingly surmises the existence of a 

 " presauripterid " type of fin, from which the original tetrapod 

 limb was evolved by the loss of the fin-rays and the disappear- 

 ance of a considerable portion of the hinder or postaxial 

 elements of the skeleton proper. A diagram — scarcely very 

 convincing — illustrates the mode in which the author believes 

 the five digits of the tetrapod limb to have been produced. 

 " Had six or seven [digits] been retained for a time," remarks 

 the author, " they would have been found too feeble to usefully 

 reach the preaxial border. Even as it is, the aquatic Amphibia 

 found the fifth useless, and it accordingly disappeared." 



In a paper on four new species of North American Palaeozoic 

 fishes Mr. L. Hussakof {Bull. Amer. Mus. Nat. Hist. vol. xxxii. 

 pp. 245-50) remarks that one is an arthrodire of the genus Dino- 

 my lo stoma ) of which it is the second known species ; the second, 

 provisionally assigned to Apateacanthus, is represented by a 

 spine with large denticules remarkable for increasing (in place 

 of diminishing) in size towards the tip. The third and fourth 

 belong to Stenacanthus. 



In 1906 Dr. Ameghino described certain sharks' teeth from 

 the Tertiaries of Patagonia as the representatives of the new 

 generic type Carcharoides ; the name alluding to the fact that 

 these teeth have sharply acuminate crowns like those of Lamna, 

 associated with the serrated margins of those of Carcharodon. 

 Teeth of a similar type from the Tertiaries of Victoria are 

 described in The Victorian Naturalist (vol. xxx., pp. i4 2- 3) by 

 Mr. F. Chapman. The discovery affords additional evidence of 



