Brown's Conchologisfs Text Book. 355 



livrer a un examen fort minutieux et tres delicat, que sem- 



bloit m'interdire l'affoiblissement de ma vue Vu mon 



age (soixante-dix ans) les entomologistes excuseront les in- 

 exactitudes que auroient pu m'echapper." 



The memoir before us, however, needed no apology, since 

 it bears all the marks of the superior intelligence of its 

 talented author. The subject of it is a small group of insects 

 to which the sugar louse (Lepisma saccharina) and the 

 ground fleas (Podurae) belong, and which are remarkable on 

 account of the circumstance of their agreeing with the true 

 insects, except that they do not undergo any transformation. 

 They form the order Thysanoura of Latreille (Thysanura 

 Leach), the peculiar structure of which had been but im- 

 perfectly noticed ; so that it is fortunate for entomology that 

 Latreille was compelled to investigate this group, especially 

 since its situation in the system of Mr. MacLeay has ren- 

 dered it so interesting. The characters of the order are 

 given at great length, of which it would be impossible to give 

 an abstract. Among these, however, the singular circum- 

 stance that these are the only insects in which aerial orifices 

 in the outer surface of the skin, named spiracles, are not 

 observable, is stated. Does not the flea exhibit the same ano- 

 maly ? Latreille divides the order into two families, — Lepis- 

 rnenae and Podurellae. In the former he only adopts two 

 genera, sinking Dr. Leach's Petrobius into a section of 

 Machilis, the characters of which are given at great length, 

 and of which he notices three species, correcting the syno- 

 nymes of the Lepisma polypoda of Linnaeus. The genus 

 Lepisma, the family Podurellae, and its two genera, Podura 

 and Synthurus, are defined; but the species of the latter 

 genera, of which those of Podura are very numerous, are not 

 noticed. These require a distinct monograph. It is remark- 

 able that only one extra- European species has been observed, 

 viz., a Lepisma from New Holland. The memoir is not 

 illustrated by figures. It occupies 27 4to pages. — J. O. W. 



Brown, Captain Thomas, F.L.S. &c. : The Conchologist's 

 Text Book, embracing the Arrangements of Lamarck and 

 Linnaeus. With nineteen steel plates bearing very numer- 

 ous engravings. Small 8vo. London. 5s. 



The chronological information afforded by shells, as found 

 deposited in the various strata of the earth, has endowed 

 these productions of nature with a degree of interest and 

 importance of which, at first sight, they seemed scarcely sus- 

 ceptible ; and they have been emphatically, as well as most 

 truly, designated the medals of creation. 



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