5 1 Bibliographical Notices, 



perceived that inasmuch ns the rhaseolotheriuin possesses forty- 

 eight teeth (four more tluui the typical number in mammals), 

 and has the strong:ly inflcxed angiihir process, it precisely fultila 

 the conditions of my argument. In point of fact, however, the 

 number of teeth is an irrelevant consideration. The other ques- 

 tion of fact relates to the structure of the Sloth's tooth : when 

 Cuvier speaks of the alternation of substance in the teeth of an 

 I'ngulate animal, he obviously refers to that peculiar alternation 

 of vertical plates of enamel, dentine and cement, which the teeth 

 of the typical Ungulates present. A difference of structure in 

 layers parallel to the crown of the tooth, is of course possessed by 

 every Carnivore, and it is this kind of arrangement which the 

 Sloth also presents. I venture to think, therefore, that this 

 objection to my argument is like most of Dr. Falconer's, and 

 to use his own words, " more specious than valid." 



I have left untouched many points in Dr. Falconer's essay, not 

 because they cannot be answered, but because I conceive they 

 will answer themselves. Under this category I leave such pas- 

 sages as those at p. 488, the singular bad taste of which will cause 

 Dr. Falconer, in his cooler moments, far more annoyance than 

 they have occasioned to any one else, exce])t his friends. But I 

 cannot pass without more grave comment, the allusion, at p. 477, 

 to the audience which I had the honour to address. Dr. Fal- 

 coner's apparent ignorance of the nature of the Friday evening 

 audience at the Royal Institution — one which the best men in 

 this country approach gravely and earnestly, knowing as they 

 do that, w hatever be the " mixture " of their hearers, there is 

 pretty sure to be among them a fair jury of their peers, — can 

 be his sole excuse for the tone of his remarks. 



BIBLIOGRAPHICAL NOTICES. 



The Ferns of Great Britain, illustrated hy J. E. SowERBY. The 



Descri/jtions by C J oiiJ<soT<i. London, Sowerby, 1855. 8vo. 

 The Ferns of Great Britain and their Allies. By Anne Pratt. 



Loudon, Society for Promoting Christian Knowledge. 8vo. 

 The Fern-Allies, illustrated hy J. E. Sowerby. The descriptions 



/>y C. Johnson. London, Sowerby, 185G. 8vo. 

 British Poisonous Plants. By C. Johnson. London, Sowerby, 



IS.^e. 12mo. 



It has seemed more convenient to notice the above books conjointly, 

 for the first three of tlicm treat upon the same subject. Our pages 

 (xv. 354) have already contained a recommendation of Sowerby's 

 • Ferns ' to the favourable consideration of botanists, and we should 

 not have thfutrJii it lu-cessary to record the fact, that its proprietor 



