December 29, 1910] 



NATURE 



265 



tion, but, owing: to the separation of their constituent 

 elements, the details of the osteologrv- can be studied, 

 except in the case of the skull, which is often badly 

 crushed, as if they belonged to modern reptiles. It 

 should be added that this full acquaintance with the 

 osteolc^y of these saurians is largely due to the 

 extreme care exercised by Mr. Leeds in extracting 

 them from the matrix. 



The remains are generally supposed to have been 

 laid down in rather deep water, but the association 

 of the marine forms with terrestrial dinosaurs, and 

 perhaps also the occurrence* of masses of lignite, sug- 

 gests that the deposit was formed near a coast, and 

 not improbably represents the mud-banks in the delta 

 of a mighty river. Here Ophthalmosaurus, the single 

 and most highly specialised representative of the ich- 

 thyosaurs, with its powerful caudal fin, pointed 

 head, enormous eye, and porpoise-like body, probably 

 lived in the open sea, where it played the part now 

 assumed by whales and grampuses. Why this par- 

 ticular type should have become practically edentulous, 

 whereas its upper Cretaceous successors were remark- 

 able for their powerful dentition, is somewhat difficult 

 to understand, although, as Dr. Andrews suggests, 

 this feature was probably connected with the nature 

 of its food. Certain features in its organisation sug- 

 gest that it was capable of " sounding " to consider- 

 able depths. 



In marked contrast to the movements of this ich- 

 thyosaur were those of the contemporary plesiosaurs, 

 which were far more specialised types than their fore- 

 runners of the Lias. Instead of being driven through 

 the water by the screw-like action of a powerful tail- 

 fin, these appear to have rowed themselves on or near 

 the surface by means of their strong paddles, of which 

 the hind pair was nearly equal in capacity to those 

 in front, whereas the tail was short, and provided, at 

 most, with a rudimentary fin. Their whole organisa- 

 tion indicates that they haunted the neighbourhood of 

 the coasts, whereas their short-necked and more 

 strongly built relatives the pliosaurs may be assumed 

 to have ventured further out to sea, although they 

 did not possess the truly pelagic habits of the whale- 

 like ophthalmosaur. The littoral habits of the plesio- 

 saurs exposed them to much more varied conditions of 

 life -than was the case with the last-named reptile; 

 and it was these diverse conditions which prob- 

 ably led to the differentiation of the group into the 

 numerous types so well described in the volume before 

 us. 



To follow the author through his survey of the 

 osteology of the groups forming the subject of this 

 volume would demand much greater space than the 

 editor is disposed to grant. Attention may, however, 

 be directed to the figure on p. 12 illustrating, the 

 form and arrangement of the constituent bones of the 

 occipital region of the ophthalmosaurian skull, and 

 more especially to the remarkable position and rela- 

 tions of the opisthotic and stapes. The great length 

 of the parasphenoid element (p. 15) is also noteworthy, 

 while of even greater interest is the author's reference 

 of the ichthyosaurian humerus to its proper side of the 

 •^^^y (P- 52). Among the plesiosaurs it must suffice 

 to refer to the determination of the relations and form 

 NO. 2148, VOL. 85] 



of the clavicles and interclavicles, and especially the 

 gradual waning of the latter (compare Figs. 61, 62, 

 70, 88). 



Dr. Andrews has a good deal to say as to the 

 phylogeny of the ichthyosaurs, for which readers 

 must refer to the work itself ; that of the plesiosaurs 

 and pliosaurs is reserved for the second volume, 

 which we hope to welcome before many months are 

 past. 



(2) Passing on to the guide-book to the fossil reptile 

 and fish galleries, the mere fact that a new edition 

 has become necessary after the lapse of only five years 

 from the issue of its predecessor (which was entirely 

 re-written), affords sufficient evidence that the work 

 meets the requirements of the class of visitors for 

 whom it is intended. As we are told in the preface, 

 the new edition is practically a replica of the eighth 

 issue, and therefore demands no special notice in this 

 place. It may be noticed, however, that the price has 

 been raised from sixpence to ninepence, at which 

 figure the work is still a marvel of cheapness. In 

 the next edition it might be well to explain the mean- 

 ing of " type " specimens (vide preface), of which the 

 general public has no conception, and like wise to 

 amend the legend to Fig. 39, which states that the 

 specimen belongs to a small tortoise, whereas it is 

 reallv something like twentv inches in length. 



R. L. 



ELECTRO-CARDIOGRAMS. 



Das Elektrokardiogramtn des gesunden and kranken 

 Menschen. By Prof. Friedrich Kraus and Prof. 

 Georg Nicolai. Pp. xxii + 322. (Leipzig: Veit and 

 Co., 1910.) Price 12 marks. 



THE electrical phenomena of the living heart has 

 been a fascinating study among physiologists 

 since the early days of electro-physiology ; information 

 has been gathered with greater and greater accuracy 

 as apparatus and methods of investigation became 

 more and more refined, and now the regis- 

 tration of the electrical changes in the heart 

 may be, and is, practically employed in the 

 diagnosis of heart affections in the wards of the 

 hospital. A full discussion of the origin and progress 

 of method in this direction is given in this book, 

 which has been produced by authors well acquainted 

 practically with all the details of this branch of physio- 

 logical and clinical inquiry. The progress of research 

 is strikingly shown in a bibliography at the beginning 

 of the work containing a list of 243 papers on the 

 subject, of which no fewer than 131 have appeared 

 since the beginning of 1900. 



It is interesting to notice that investigations into the 

 electrical phenomena of the heart are associated at 

 different periods with the invention of special instru- 

 ments and methods, such as the galvanometers of 

 Matteucci and du Bois Reymond, the differential rheo- 

 tome of Bernstein, the capillary electrometer of Lipp- 

 mann, and, still more recently, the string galvano- 

 meter of Einthoven. Matteucci, in 1843, was the 

 earliest observer with the galvanometer ; then, in 1849, 

 followed du Bois Reymond with his bussole ; Kollker 



