• First pleopod lacking cephalic process (Figs. 81c-f, 82):...............................................................  3

2(1).   Hooks on ischia of third and fourth pereiopods well developed (Fig. 4c; see also Fig. 81a):.....
           ........................................................................................................  Fallicambarus macneesei  (Black, 1967).

       (Pools and roadside ditches and probably burrows in the Calcasieu River system in
        Calcasieu Parish, Louisiana.  Literature:  Black, 1967).

• Hooks on ischia of third pereiopods; hooks on fourth vestigial or absent (Fig. 4a; see also Fig. 81b):..
  ...........................................................................................................  Fallicambarus strawni  (Reimer, 1966).

       (Simple and complex burrows in Howard County, Arkansas.  Literature:  Reimer, 1966).

Fig. 81.  Lateral view of left first pleopods.  a, Fallicambarus macneesei;  b, F. strawni;  c, F. dissitus;  d, F. hortoni;  e, F. byersi;  f, F. oryktes.  (cp, cephalic process).

3(1).   Central projection of first directed strongly proximomesially, sometimes crossing that of other
            member of pair (Figs. 81c, 82d):...............................................  Fallicambarus dissitus  (Penn, 1955).

       (Burrows in Caldwell and Lincoln parishes, Louisiana.  Literature:  Penn and Marlow, 1959).

• Central projection of first pleopod directed caudally or caudoproximally, never directed mesially
  or crossing that of other member of pair (Figs. 81d-f, 82a-c):..............................................................  4

Fig. 82.  First pleopods.  a-c, Lateral view of left first pleopods.  a, Fallicambarus uhleri;  b, F. fodiens;  c, F. hedgpethi;  d, Caudal view of first pleopods of F. dissitus.

4(3).   Central projection subtruncate, broad distally, and directed caudally (Fig. 81d):...............................
           .....................................................................................  Fallicambarus hortoni  Hobbs and Fitzpatrick, 1970.

       (Burrows in the Hatchie River drainage, McNairy County, Tennessee.
         Literature:  Hobbs and Fitzpatrick, 1970).

• Central projection tapering and directed caudoproximally (Figs. 81e-f, 82a-c):..................................  5

Fig. 83.  Chelae.  a-d, Dorsal view;  e, Lateral view.  a, Fallicambarus oryktes;  b, F. uhleri;  c, F. fodiens;  d, F. hedgpethi;  e, F. byersi.

5(4).   Distal 1/2 of cephalic margin of first pleopod inclined caudally at angle of approximately
           30 degrees (Fig. 81e);  ventral surface of propodus of chela with longitudinal row of long
           stiff setae near lateral margin (Fig. 83e):......................................  Fallicambarus byersi  (Hobbs, 1941).

       (Burrows from Hancock County, Mississippi, eastward to Okaloosa County, Florida.
         Literature:  Hobbs, 1942b).

• Distal 1/2 of cephalic margin of first pleopod inclined caudally at angle of less than 20
  degrees (Figs. 81f, 82a-c);  ventral surface of propodus of chela without longitudinal row
  of long stiff setae near lateral margin.....................................................................................................  6

Fig. 84.  Lateral view of carapaces.  a, Fallicambarus uhleri;  b, F. fodiens.

6(5).   Mesial margin of dactyl of chela with irregularly arranged tubercles along proximal 1/2 but never
           with subserrate row (Fig. 83a; see also Fig. 81f):................................................................................
           ...........................................................................................  Fallicambarus oryktes  (Penn and Marlow, 1959).

       (Burrows in St. Tammany Parish, Louisiana, and southern Mississippi.
         Literature:  Penn and Marlow, 1959).

• Mesial margin of dactyl of chela with subserrate row of tubercles along at least proximal 1/2
  (Fig. 83b-d):................................................................................................................................................  7

Fig. 85.  Caudal view of third maxillipeds.  a, Fallicambarus uhleri;  b, F. fodiens.

7(6).   Areola usually constituting less than 39 per cent of entire length of carapace;  rostrum subplane
           dorsally and only moderately deflexed anteriorly (Fig. 84a);  proximolateral 1/2 of postaxial surface
           of ischium of third maxilliped with many hirsute punctations mesial to lateral row (Fig. 85a; see
           also Figs. 82a, 83b):.........................................................................  Fallicambarus uhleri  (Faxon, 1884).

      (Burrows, streams, and lentic habitats in the coastal plain from Maryland to South Carolina.
        Literature:  Meredith and Schwartz, 1960).

• Areola usually constituting more than 39 per cent of entire length of carapace;  rostrum concave
  dorsally and strongly deflexed anteriorly (Fig. 84b);  proximolateral 1/2 of postaxial surface of
  ischium of third maxilliped with few, if any, hirsute punctations mesial to lateral row
  (Fig. 85b):...................................................................................................................................................  8

8(7).   Hump on mesial process of first pleopod obscuring part of central projection in lateral aspect
           (Fig. 82b);  central projection with subapical notch (often abraded in middle to late intermolt stages);
           opposable margin of fixed finger of chela with only 1 tubercle markedly larger than others
           (Fig. 83c; see also Figs. 84b, 85b):...............................................  Fallicambarus fodiens  (Cottle, 1863).

       (Burrows, streams, and lentic habitats from lower Ontario, Michigan, Ohio, Indiana, Illinois
         southward to Arkansas and southwestern Georgia.  The ranges of this species and the
         closely allied F. hedgpethi appear to overlap in Tennessee.  Literature:  Crocker and Barr, 1968).

• Hump on mesial process of first pleopod never obscuring part of central projection in lateral aspect
  (Fig. 82c);  central projection lacking subapical notch; opposable margin of fixed finger with 2 major
  tubercles (Fig. 83d):......................................................................  Fallicambarus hedgpethi  (Hobbs, 1943).

       (Burrows and tenporary bodies of water from Texas to Tennessee.
         Literature:  Penn, 1959;  Penn and Hobbs, 1958).