June 26, 1896.] 



SCIENCE. 



913 



dermal plate enclosing the upper or lower 

 division of the muscle plate of either side ' 

 (p. 26). It is not evident what reason he 

 has for such a belief, and whj^ the extension 

 of single plates is not more probable ; equally 

 improbable is the explanation of the size of 

 the ' dermal plates of the Seahorse ' result- 

 ing from ' fusions ' (p. 26). As a rule, en- 

 larged scales result from individual exten- 

 sion, and not general aggregation. The 

 mode is suggested by the varieties of carp 

 alluded to by Dr. Dean (p. 26). 



A short chapter on ' the development of 

 fishes' is given, and, on the whole, the sub- 

 ject is well brought up to date. Dr. Dean 

 thinks that the data of embryology are 

 ' very inconclusive ' with reference to the 

 successively increasing complication of 

 structure, if at present in any way suggest- 

 ive (p. 180). This is certainly the case if 

 reference is had only to external features. 

 ' Adaptive characters have entered so 

 largely into the plan of the development of 

 fishes that they obscure many of the features 

 which might otherwise be made of value for 

 comparison' (p. 180). Such being the case, 

 we have no right to expect very much from 

 superficial characters. It is the study of 

 the anatomy, and especially of the develop- 

 ing bones, that will ultimately give useful 

 hints. Indeed, only from a survey of the 

 detailed comparative anatomy of the suc- 

 cessive stages of the developing fishes have 

 we a right to look for light on some ques- 

 tions of relationship and ph3'logenj\ For 

 instance, we should not expect much more 

 guidance from mere externals of the various 

 stages of ' Ceratodiis ' than the illustrations 

 actually give. Here it may be added that 

 we are indebted to Dr. Dean for giving the 

 results of such very recent work as that of 

 Semon. 



The nomenclature of Dr. Dean's work is 

 mostly in accord with current American 

 usage, so far as the American species at 

 least are concerned, but sometimes that cur- 



rent in Europe is adapted, as Bdellostoma 

 (61) instead of Septatrema, Cestracion (85), 

 for Heterodontus, Lcemargiis (91) for Som- 

 niosiis, BMna (91) for Squatina, 'Butrinus' 

 (258, 260, Butirinus') for Alhula, etc. Some- 

 times there is a discrepancy resulting, per- 

 haps, from the fact that the author may not 

 have been fully aware that his names re- 

 ferred to the same form as Squalus (89) and 

 Aeanthias (216). 



The numerous (344) figures are generally 

 well selected and illustrate morphological 

 and other data. Some, however, as most 

 derived from Agassiz's and Pander's works 

 and that of Pleuracanthus (90), might have 

 been supplanted by later and better ones. 

 A few, also, have been misplaced or mis- 

 named, as 29, which really represents 

 Aetobatus and not Trygon ; 172 depicting 

 Bathyonus compressus; 173 representing Nota- 

 canthus sexspinis; 174 representing Parali- 

 paris hathyhius, and 182 illustrating Miero- 

 gad'us tomeodus and not Gadus morrhua. 



The most serious omission in the ' Fishes, 

 living and fossil,' is of most of the living 

 forms. Somewhere near 10,000 of those 

 are Teleosts, and only about 350 living 

 species belong to the other divisions. Nev- 

 ertheless the systematic consideration of 

 the Teleosts is condensed within 13 pages 

 (165-178), and no idea is given of the range 

 of variation and the diversity of that large 

 group. The Cyprinoideans, the Characinoi- 

 deans, the Cichloideans and the Percoi- 

 deans, Avhich constitute so large an element 

 of fresh-water fishes, are not even mentioned 

 as such. In the tables of ' classification ' 

 and ' distribution * * * in geological time ' 

 (pp. 8, 9) only six groups (Teleocephali, 

 Clupeoids, Salmonids, Perches and Berycids, 

 Siluroids, and ' G-adoids and other Teleosts') 

 are named. Surelj' the student would rea- 

 sonably expect to find more in a work en- 

 titled as it is. 



Mention having been made of the ' Teleo- 

 cephali,' it may be added that the group 



