Bihliographical Xoticea. 449 



Hard parts of great complexity have thus arisen, offering to him 

 who can decipher tlieir story clues as valuable for the construction 

 of genealogical lines as have been found in the limb-hones of 

 luammals or the hinge-teeth of bivalve moUusks." Attention has 

 also been paid to the development of the gills, foot, and girdle, 

 '• and for the first time systematic use has been made of the sense- 

 organs of the shell (tegnmentum), and the system of sculpture of 

 the latter." It is curious that the radula, which, as a rule, furnishes 

 such important ordinal characters among the (iastropoda, presents 

 but very slight variations in the Chitons, and is of no assistance in 

 the classification of tlie group. 



The rest of the volume consists of detailed descriptions of the 

 families, genera, and species, which are illustrated by sixty-eight 

 carefully executed plates, giving figures, of which nearly three 

 hundred are original, of the exterior of the shells, the disarticulated 

 valves, showing the insertion-plates, slits, and sculpture. 



One of the most radical changes in the classification proposed by 

 Pilsbry is the abandonment of the groups of regular and irregular 

 (Jhitous. He arranges them into three principal divisions, namely 

 I'^oplacophora, Alesoplacophora, and Teleoplacophora. In the first 

 tht vdlvis lack itisertion-jilates, or^ if present, tliey areunslit. In the 

 second all valves possess insrriion-plafes, but are without e^fes ; valves 

 i., i.-vii., or i.-viii. have slits ; teeth smooth or but sli<j]itly roughened 

 between the slits, never closeh/, finely peetinated. In the third all 

 valves, or valves i.-vii., i^osse^s insertion- (Aates cut into teeth by slits ; 

 the teeth are sharply sculptured or '■'pectinated" outside by fine 

 vertical grooves. 



These three " superfamilies '" are again subdivided into families, 

 subfamilies, genera, and subgenera. 



The study of the Chitons is an exceptionally complex one, and 

 therefore, considering the rapidity with which the work has been 

 produced and the newness of the subject to the author, Mr. Pilsbry 

 is to be congratulated upon the result of his labours in the mono- 

 graph before us. In conclusion, it is satisfactory to observe that 

 this work has done good service in putting a definite specific value 

 upon the large number of manuscript names proposed by Carpenter 

 wliich have in the course of the last twenty years found their w'ay 

 into many collecticus throughout the world. 



Life and Rod: By R. Lydekker, B.A., F.G.S., F.Z.S., «S:c. 

 8vo. London, 1894. 



Tuis popular exposition of facts and theories relative to some warm- 

 blooded and some cold-blooded back-boned animals, and some few 

 shells, insects, sea-urchins, and others, consists of various essays 

 that have been already before the public in periodicals, and are now 

 arranged in twenty-one chapters, with sixty-three illustrations. 

 Elephants, moles, porcupines, whales, deer, sheep, lemurs, arma- 

 dillos, crocodiles, some fishes, and other representative animals are 



Ann. cO Ma^. 2\. Hist. Ser. 6. Vol, xiii. 30 



