404 R. E. BUCHANAN 



Micromyces Gruber, 1891, p. 648 



not Micromyces Dangeard, 1888, p. 55 

 Nocardia Trevisan, 1889, p. 9 

 Streptothrix Cohn, 1875, p. 186 



not Corda, 1839 

 Thermoactinomyces Tsilinsky, 1899, p. 500 

 Rasmussenia De Toni and Trevisan, 1889, p. 930 



The genus Actinohacterium has had no definite specific names 

 ascribed to it. 



The following are invalid because previously used for other 

 distinct groups of organisms: Micromyces and Streptothrix. 



The name Actinocladothrix was used by Affanassieff in the 

 combination Bacterium actinocladothrix, but several authors 

 have listed the name as though it had been used as a genus. 



The following generic names are therefore to be considered, or 

 at least are not invalid for any of the preceding reason: Actin- 

 obacillus, Actinomyces, Cohnistreptothrix, Discomyces, Lepto- 

 trichia, Nocardia, Thermoactinomyces, Rasmussenia. 



The genera may be differentiated by the following key. 



Key to the genera of Actinomycetaceae 



A. No evident aerial threads or conidia formed. Usually parasitic. Often 



anaerobic or microaerophilic. 



1. Threads usually not branched. 



a. Threads disjointing very readily; long mycelial threads uncommon. 



Genus 1. Actinobacillus 



b. Threads longer, not disjointing into short rods. 



Genus 2. Leptotrichia 



2. Threads more or less branched, frequently clubbed in tissues. 



Genus 3. Actinomyces 



B. Aerial threads and conidia evident on culture media Genus 4. Nocardia 



Genus 1. Actinobacillus Brumpt, 1900, p. 849 



Filament formation; resembling streptobacilli. In lesions no 

 mycelium formed, but at peripheries finger shaped branched cells 

 are visible. Gram negative. Not acid fast. 



Possibly the genus belongs with the Bacteriaceae. It is evi- 

 dently a transition form. 



