INTEODUCTION. 



11 



He characterises the Thysanura as possessing " Os 

 mandibulis, palpis, labro et labio, corpus saepius squa- 

 mosum aut liirsutum, errans, ano setoso caudave 

 furcata. Insecta cursu veloci, vel saltatorii." 



He divides the Thysanuea into two famiUes :^ 



Ordo Primus. 

 Tliysanoura. Thyscmoures. 



C Palpi exserti, elongati : an ten- "\ Faviilia prima. 

 nee a basi ad apicem multiarticu- f — 



latse, articulis innumeris, brevissi- t Lepismense. 



mis ; Cauda setis tribus exsertis. J Lepismenes. 



Thysanoura < 



Palpi nee exserti, nee facile con-"^ Familia secunda. 

 spicui : antennte articulis paucis, | — 



aut apice tantum multiarticulata) ; J- Podurellse. 

 Cauda furcata, sub abdomine in- Podurelles. 



^flexa. 



Subsequentlyin 1810^ he placed theTHYSANURAbetween 

 the Myeiapoda and Parasita, as the third order of the 

 Aeachnida. He distinguished two genera of Lepismidce, 

 Lepisma and Machilis, and two of Poduridm, separating 

 the globular species under the name of Smyntliurus, 

 which has since been generally adopted. 



Lamarck, in his ' Animaux sans Vertebres,' adopts 

 the group Thysanuea, of which, however, he only 

 mentions six species, namely, Smynthurus fuscus, 8. 

 viridis, and S. signatus, Podura aquatica, P. villosa, 

 and P. plumhea. 



The ' Journal of the Academy of Philadelphia' for 

 182tP" contains a short paper by Mr. Say on the 

 Thysanuea of the United States. Besides a species of 

 Machilis, he describes three species of Podura and one 

 of SmyntliuTus. He gives, unfortunately, so few par- 

 ticulars that it will probably not be very easy for 

 American naturahsts to identify them, nor is it, I 

 think, possible even to conjecture how far they are 

 distinct from our European species. His P. iricolor is 



^ ' Genera Crustaceorum et Insectorum.' 



- ' Considerations generales sur I'ordre naturel des Crustaces, des 

 Aracbnides et des Insectes.' 



