834 A. E. Verrill — Decapod Crustacea of Bermuda. 



Percnon planissimum (Herbst), M. J. Rathbnn. Flat Crab. 



Cancer planissimus Herbst, Natiirh. Krabb., p. 3, pi. lix, fig. 3, 1804. 

 Acanthopus 2)Ianissimus Stimpson, op. eit , p. 104 [242], 1860; Crust. N. 



Pacific Expl. Exp., Smithsonian Misc. Coll., xlix, p. 123, 1870 (1907). (descr. 



colors) Bonin Is. 

 Acantho2ms Gibhesii Milne-Edw., Mel. Carcin , p. 146. 

 Leiolophus planissimus Miers, Catal. Crust. N. Zealand, p. 46, 1876. 

 Percnon planisnimum Rathbnn, Dec. Crust. W. Africa, Proc. U. S. Nat. Mns., 



xxii, p. 281, 1000 ; Brach. and Macr. Porto Rico, p. 19, 1901. Verrill, 



these Trans., vol x, p. 575, 1900. 



Plate X, Figure 8. Plate XII. Figure 4. 



Easily recognizable on account of its very flat, smooth body, and 

 the slits in the front and in the eye-sockets. Its structure is admira- 

 bly adapted to its habit of living in the confined spaces under stones. 



In life the carapace is usually variegated or mottled with brown, 

 pinkish flesh-color and salmon ; there is generally a median longitu- 

 dinal stripe of bright pale blue ; the legs are banded with reddish 

 brown and light ])ink. Ventral side of body pale blue ; of legs 

 pale pink (C. S. V.). 



One female taken in April, 1901, carried eggs ; also one taken in 

 midsummer, by Prof. Kincaid. 



Measurements of Bermuda specimens. 



The chelae are feeble in the females but large in the males. In the 

 males the two are unequal; the large chela has a large and long tuft 

 of soft hairs on inside of nierus. 



It was found very commonly by us in 1898 and 1901, on many 

 rocky shores under stones at about low-tide level. It was in the 

 collections of J. M. Jones ; G. Brown Goode ; Prof. Kincaid, 1903 ; 

 Field Museum E.vped., 1905 ; Bermuda Biological Station, 1903, and 

 others. 



It is widely distributed throughout the West Indies to Brazil. 

 Azores : Spain ; Madeira ; West Africa and South Africa ; Mauri- 

 tius to Japan, and Hawaiian Is., Bonin Is. Cape St. Lucas to Chili 

 (Rathbun). Colon (Yale Mus.). 



