NATURE 



[July 7, 1910 



graph shown. The present illustration shows the 

 sudden act of closure, by which the turning move- 

 ment is brought about, almost completed. 



Of photographs taken with the special apparatus 

 described, two illustrations are given ; the first that 

 of n |)laice larva 13 mm. in length, and magnified 



Fig. 5. — A Mysid; 



five times; the second that of a crustacean, one of the 

 Mysidacea, 2 mm. in length, magnified fifteen times. 

 This photograph shows very distinctly the two stato- 

 cvsts on the uropods or appendages of the sixth abdo- 

 minal segment, and gives a good general view of 

 the animal. 



Higher magnifications of any particular part are 

 obtained as described by slipping the microscope into 

 the apparatus. 



In addition to the above methods, the natural 

 colours of marine animals may be recorded on the 

 autochrome plate. The autochrome plate is particu- 

 larly useful when it is desired to make a permanent 

 record of a stained specimen where the staining is 

 of a fugitive character. Francis Ward. 



SOME EXTINCT VERTEBRATE ANIMALS 

 FROM NORTH AMERICA.' 



ANEW volume of collected papers, published by 

 the American Museum of Natural History, 

 New York, enables us to realise how important and 

 numerous are the additions to our 

 knowledge of extinct vertebrate animals 

 still made by systematic explorations in 

 North America. The contributions 

 now received deal with the work of 

 only four years, 1904-8, accomplished 

 bv one institution ; but they make great 

 advances in nearly all parts of the sub- 

 ject to which they relate, and their 

 value is increased by the excellent 

 text-figures and plates w-ith which they 

 are illustrated. The pioneer discoveries 

 of Leidy, Marsh, and Cope furnished 

 for many years a continual series of 

 surprises for the student of extinct 

 vertebrates ; their successors during the 

 past decade and a half have not only 

 filled in many details in the ])re- 

 liminary view thus obtained, but have 

 also been scarcely less successful in 

 recovering unexpected groups and 

 niissing links. Present explorers have, indeed, 

 the advantage of being able to pursue their 



' " Fossil Verte'^rates in the .'American Muieuiu of Natural Hislorj'." 

 Dspariment of V^rtehrate ralseomology. Vol. iii.. Articles collected from 

 the American \Ius-um Kiilletin for iht years 1904-8, by H. Faiffield Osborn, 

 &c. (Mew York, 1909.) 



NO. 2123, VOL. 84] 



work in the remote west in peaceful leisure, without 

 any armed escort, and so have facilities for deter- 

 mining the relative positions of the strata from which 

 they excavate the various fossils. In the early days, 

 with hurried traverses, there was a tendency to decide 

 ilie rel;ili\e :n;i'^ of the fossils solely by their own 

 peculiar features, without any ex.-ict 

 .bservations in the field. The re- 

 -idt was sometimes an argument in 

 a vicious circle. As shown by the 

 \olume now before us, that is all 

 clianged. We find detailed descrip- 

 tions of specimens from the 

 Permian of Texas, the L'pper 

 Cretaceous of Montana, the Eocene 

 ijf Wyoming, and the Miocene of 

 South Dakota. Accompanying them 

 are well-illustrated exact accounts of 

 all these formations and localities, 

 determining the relative ages of the 

 genera and species which were 

 obtained from them. 



The scientific work of the 

 palasontologists in the American 

 Museum is of two kinds. Part is 

 devoted to the reconstruction and 

 mounting of skeletons of general 

 interest ; part is concerned with the most 

 detailed and special research, for which it often 

 happens that not more than mere fragments are 

 available. The publications record the results in both 

 directions, and thus provide ample material, not only for 

 the specialist, but for anyone interested in the broader 

 features of natural history. It must also be added 

 that the reconstructed skeletons are prepared with 

 the greatest scientific care. The fine example of the 

 Columbian mammoth now described, for example, 

 was mounted after an elaborate study of the arrange- 

 ment of the footprints of a living elephant and the 

 attitude of its limbs when walking. The skeletons of 

 Equidae were similarly mounted after studies of the 

 living horse — especially after a studv of the Arab, to 

 which one article in the new volume is devoted. 

 .'Kmong startling mounts for which existing animals 

 give little help may be specially mentioned the re- 

 constructed skeleton of Naosaurus, which is one of 

 the primitive reptiles from the Permian of Texas not 

 hitherto found in a complete state. It is a long- 

 bodied, squat reptile, with a formidable array of 



clavigcr, by Mr. C. R. Knight. 



sabre-like teeth, and a high, thorny frill along the 

 back, which is supported by the much-elongated 

 neural spines of the vertebrte (Fig. i). Prof. Osborn, 

 who describes this specimen, is careful to explain 

 exactly on what material the various parts of the recon- 



