.Revieivs — American Palceontology. 125 



Fig. 5. A solid section across the food-groove to show the relation of 

 cover-plates to floor-plates ; based mainly on portions of 1. ant. and 1. post, 

 rays, x 5 diam. 



Fig. 6. A transection of the floor-plates, showing their relation to the 

 interradials. The tloor-plate on the left is viewed on its sutural surface, 

 which bears the pore-canal. Based on the broken regions of ant. and 

 r. ant. rays, x 5 diam. 



Fig. 7. The hydropore. The adjacent regions of the floor-plates show 

 the depression that receives the ends of the cover plates. X 10 diam. 



Fig. 8. Parts of the floor-plates and ccjver-plates near the peristome, 

 showing the accessory plates, x 10 diam. 



Fig. 9. The periproct. x 8 diam. 



Fig. 10. A section reconstructed along the line a-b in Figs. 1 and .S, 

 showing the approximate thickness of the plates and the relations of the 

 adapical hollow and lobes. Nat. size. 



Fig. 11. Part of the thin, plated integument of the adapical face. The 

 actual plates are not so clearly seen in this specimen as they are in some 

 others (cf. Plate XIV). X 20 diam. 



Plate XI. 

 Edrioaster bigsbyi. Specimen B, from drawings made in 1899 by Mr. Gilbert C. 

 Chubb. 



Fig. 1. Adoral face, with the posterior interradius towards the observer. 

 Cover-plates are preserved in all the rays, but are pressed into the grooves. 

 X 2 diam. 



Fig. 2. The adcentral region of the posterior interradius, showing the 

 hydropore. x 10 diam. 



Plate XII. 

 Edrioaster levis. Holotype (Brit. Mus., E 15900). x 2 diam. These photo- 

 graphs were taken under water, so as to bring up the sutures and the 

 fragments of plates, which are seen with much difficulty in the dry state. 



Fig. 1. Adoral face. The small periproctals are seen depressed in the 

 posterior interradius, next the observer. 



Fig. 2. Adapical face. This shows the peripheral course of the 

 grooves. The frame and the plated integument within it cannot be 

 distinguished. 

 Note. — The explanation of Plates XIII and XIV will be given with those 

 Plates in the next Number. 



(To be continued.) 



I. — American Palaeontology. A Review.^ 



rPHE true founders of Palaeontology, Lamarck and Cuvier, were 

 JL interested in fossils simply as the relics of once living animals. 

 Both compared their specimens with recent types ; both from these 

 comparisons drew philosophical conclusions, and established broad 

 principles intended to apply to all animals, living or dead. 



^ Palaeontology. By H. F. Osborn, with the co-operation of A. W. Grabau. 

 EncyclopcEdia Britannica, 11th ed., pp. 579-91. 



The Continuous Origin of certain Unit Characters as observed by a Palaeonto- 

 logist. By H. F. Osborn. Reprinted from the Harvey Lectures, ser. 1911-12, 

 of the Harvey Society of the United States. 



Cenozoic Mammal Horizons of Western North America. By H. F. Osborn, 

 with Faunal Lists of the Tertiary Mammalia of the West by W. D. Matthew. 

 U.S. Geol. Surv., Bull. 361, 1909. 



