1002.] AND ANCIENT GEOGRAPHY. 277 



ized one, and its distribution is more sharply limited than that of 

 Potamobius^ it being found only in the eastern parts of North 

 America, Mexico and Cuba. 



Genus : Caryibai'us Er. 



The genus Cambarus contains at present sixty-six well-known 

 species ; of a sixty-seventh, the group to which it belongs is doubt- 

 ful {C. clypeatus Hay, Missouri). The species form five groups 

 within the genus. 



Sixteen species belong to the first group, namely : 



1. blandingi {Yi2C[\.). 9. versuiiis l^d.g. 



2. hayiYz.yi. 10. spicu/ifer (Ltc). 



3. fallax Hag. 11. pellucidus (Tell.). 



4. clarki 0\x. 12. acheroniis\^o^Vivi}o. 



5. troglodytes (Lee). 13. wiegmanni^x. 



6. lecontei Hdig. 14. alleniYd^y.. 



7. angustatus (J-,Qc.). 15. evermanni YdiX. 



8. piibescens Fax. 16. penicillatus (Lee). 



Eight species belong to the second group : 



1. cubensis Er. 5. gallinus Cock, and Port. 



2. carinatus Fax. 6. gracilis Bund. 



3. ?nexica7ius Er. 7. carolinus Er. 



4. simulans Fax. 8. advena (Lee). 

 To this group possibly belongs clypeatus Hay. 



Thirteen species belong to the third group : 



1. acuminatus YdiX. 8. tihleri Ysiyi. 



2. bartoni (Fabr.). ' 9. setosus Fax. 



3. longulus Gir. 10. extraneus Hag. 



4. latimanus (Ltc). 11. Jordani YsiX. 



5. dubiusYsiX 12. cornutusYd^y.. 



6. diogenes Gir. 13. ha?nulatus Cope and Pack. 



7. argillicola Fax. 



generic name of Astactis M. E., claim that Latreille (Consider, gener., etc., 

 1810; see Faxon, 1898, p. 662) has made this species, Astacus fluviatilisYz}ox., 

 the type of the genus Astactis Fabr. This statement of Latreille, however, is 

 erroneous, since Astacus of Fabricius is a genus without type, and remained such 

 until Saniouelle (^The Entomologists'' Useful Compendium, i8i9,p. 95) separated 

 Astacus and Potamobius (Lobster and Crayfish). See Faxon, 1885 ; Ortmann, 

 «« Das System der Decapodon Krebse " (^Zool. Jahrb. Syst., Vol. 9, 1896, 

 p. 430), and Stebbing (in Natural Science, Vol. 12, 1898, p. 239 fif.). 



