418 PROCEEDINGS OF THE NATIONAL MUSEUM vol.89 



Measurements. — The holotype: Carapace, height 1.26, width 1.27, 

 length 2.65 cm.; areola, width 0.20, length 0.84 cm.; rostrum, width 

 0.35, length 0.51 cm.; abdomen, length 3.00 cm.; right chela, inner 

 margin of palm 0.82, width of palm 0.85, outer margin of hand broken, 

 length of movable finger 1.14 cm.; carpus of first pereiopod (right), 

 length 0.82, width 0.61 cm. The allotype: Carapace, height 1.47, 

 width 1.39, length 2.92 cm.; areola, width 0.20, length 0.97 cm.; 

 rostrum, width 0.35, length 0.51 cm.; abdomen, length 3.29 cm.; 

 right chela, inner margin of palm 0.66, width of palm 0.73, length of 

 outer margin of hand 1.78, length of movable finger 1.07 cm.; carpus 

 of first pereiopod (right), length 0.76, width 0.50 cm. 



Type locality. — Near the Yellow River at Milligan, Okaloosa County, 

 Fla., at intersection of State Highway No. 41 and U. S. Highway No. 

 90. The crayfish were dug from simple burrows in the roadside ditches. 

 The burrows ranged in depth from 1 to 2 feet, reachmg the water-table 

 6 inches to a foot below the surface of the ground. Several of the 

 burrows were open, though the majority of them were marked by 

 low, closed chimneys. The soil is a sandy-clay mixture, and the 

 ground is covered with a thick mat of grass. Some sections of the 

 ditch held water, but at this time most of it "was dry. The specimens 

 were collected on April 4, 1938. 



The male holotype (form I) and the female allotype (No. 76595) 

 and a male paratype (form II) are deposited in the United States 

 National Museum. Of the paratypes, a male (form II) and a female 

 have been deposited in the Museum of Comparative Zoology; a male 

 (form II) and a female in the University of Michigan Museum of 

 Zoology; a male (form I), two males (form II), and six females have 

 been retained in my own collection. 



Belationships. — A rostrum without lateral spines, a broad areola, and 

 a rather short, thick body are characteristic of four Florida crayfishes: 

 Cambarv^ barbatus, 0. hubbelli, C. kilbyi, and C. rathbunae. Peculiar to 

 C. rathbunae and C. hubbelli is the presence of hooks on the ischiopo- 

 dites of only the third pereiopod; however, in C. rathbunae the ischio- 

 podites of the fourth pereiopods bear a tubercle which suggests a 

 rudimentary hook. Peculiar to C. rathbunae and C. kilbyi is the lack 

 of the barbate condition on the palm of the chelae in the male. It is 

 to be noted that the first pleopod of O. rathbunae is much more like that 

 of C. barbatus than that of C. hubbelli or C. kilbyi. 



It is a pleasure to name this species for Dr. Mary J. Rathbun, 

 Associate in Zoology in the United States National Museum. 



