158 SOME NEW BOOKS [February 



especially the Purbeck and Como types as representing only Monotremes ami 



.Marsupials ; and from this we infer that he considers the Eutheriaor Placentals 

 of comparatively late origin. A few errors have found their way into the treat- 

 ment of the mammals, which may be corrected in a later edition. The teeth of 

 Ancylopoda (page 307) are said to resemble those of the Rhinoceros. This is 

 evidently incorrect, as they stand nearest the teeth of the Titanotheres, and 

 hence of the Artiodactyls. Erroneously, we believe, the author follows Lydekker 

 and Flower in placing all the early Perissodactyla among the Lophiodontidae, 

 disregarding the fact that in the Lower Eocene all the modern families of 

 Perissodactyls are sharply defined. This leads to a further confusion in 

 reference to the family Palaeotheriidae, which is said to approach the Rhino- 

 ceroses. The conception of the family distinctness of early ungulates agrees 

 with that held by the author himself in his treatment of the Fishes, namely, 

 that family lines should correspond with phyla, and not with the parallel 

 assumption by distinct phyla of similar characters. 



One of the most remarkable things about this work is, that the author 

 appears to be less clear and logical in the major classification of the Fishes, his 

 own special field of work, than he is among the Reptiles. This appears to arise 

 from far too great reliance upon the lines drawn by Reichert and Huxley 

 between "autostylic" and "hyostylic" types, and from setting aside the really 

 fundamental characters of division between cartilaginous fishes in which true 

 bone is absent, and Teleostomes and Dipnoans, which have more or less true 

 bone. Single characters, such as the suspensorium, may be safely employed in 

 major classification, provided first that they are not acquired by parallelism, and 

 second that they really afford sharp and natural lines of division. Hyostylism 

 and autostylism answer neither of these criteria. The Elasinobranchs are 

 grouped by the author as hyostylic (p. 27), although members of this sub-class 

 show every stage of transition between autostylism (Heptanchus) and hyo- 

 stylism (Raja). These transitions are obviously adaptations to feeding habits, 

 analogous to those which we observe among reptiles with a loose or swinging, 

 and tight or firm, articulation for the angle of the lower jaw. The autostylic 

 Chimaera, with its firmly united upper jaw and reduced hyomandibular, is 

 adapted to a mode of feeding upon small molluscs and crustaceans not very 

 dissimilar from that of the lizard Sphenodon, in which the food is firmly seized 

 by the anterior teeth and cut up by the molar plates. The loose and swinging 

 shark jaws, with the hyomandibular acting as a supporting bar, are to be com- 

 pared with those of snakes, in which the mouth is very expansible, and the food 

 is swallowed whole, the backward - pointing teeth serving to prevent escape. 

 Moreover, these terms are misapplied by the author not only in sharks, but in 

 other specific cases. The Crossopterygians (p. 69) are defined as " hyostylic " 

 (a character by the Avay which would seriously interfere with their position 

 among the ancestors of the pronouncedly autostylic Amphibia), and this is an 

 error, for, as observed by Pollard, " On examining the hyomandibular it will be 

 seen that it can take very little part in the suspension of the jaws." 



We thus conclude that a close examination of the suspensorium of all the 

 living and extinct fishes proves that "auto-," " hyo-," and " amphistylism " are 

 at the most ordinal characters, and cannot take rank as sub-class characters, 

 except in the definition of the Dipnoi. Even then some of the orders are 

 susceptible to adaptive modification, and thus do not present those sharp and 

 fast lines of demarcation which are necessary for ordinal definition. To return 

 to Chimaera, it is obvious that; so far as the concrescence of the palatoquadrate 

 of the skull is concerned, this condition could readily be derived from that seen 

 in the Notidani (Heptanchus) simply by fixation, and after carefully comparing 

 all the other characters which are assigned by the author to give Chimaera ami 

 its allies a sub-class position, among the Holocephali, we find that they are no 

 greater than those which give the Acanthodii and Pleuropterygii their ordinal 

 position. Upon these grounds we conclude that the scheme of major classifica- 



