GEOLOGY AND PALEONTOLOGY OP THE CANAL ZONE. 175 



part of Culebra formation. Oligocene series. D. F. MacDonald 

 and T. W. Vaughan, collectors. 1911. Station 6012c. 



Holotype.— Cat. No. 324226, U.S. KM. Propodus of right and 

 major cheliped with only the base of the immovable finger remaining. 

 Palm swollen. In side view the upper and lower margins are arcu- 

 ate, the palm narrowing considerably toward the wrist. Surface 

 smooth. At the distal end above the lower margin there is a deep 

 groove which is prolonged on the finger. The palmar tooth which 

 overlaps the dactylus is present; also 4 prehensile teeth of the fixed 

 finger, arranged in 2 transverse rows on the upper surface, the outer 

 tooth of the distal pair being much the largest. 



Measurements.— Length of palm, to sinus, 6.5 mm. ; height, 4.3 

 mm. ; thickness, 2.7 mm. 



This specimen has the general form of E. nitida Stimpson, 1 a Re- 

 cent species occurring on the coast of the Gulf of Mexico and the 

 West Indies. I have no example of the Panamian species, E. polita 

 Smith 2 for comparison. E. nitida is considerably larger than the 

 fossil form, the fixed finger is somewhat wider at the base but it has 

 the 4 basal teeth similarly disposed ; the proximal end of the upper 

 margin is thinner and more acute than in E. culebrensis. 



Subfamily Hexapodinae. 



Living representatives of this subfamily are restricted to the Indo- 

 Paeific region. 



Genus THAUMASTOPLAX Miers. 



TJiaumastoplax Miers, Ann. Mag. Nat. Hist., ser. 5, vol. S, 1881, p. 261. 

 The generic position of the species placed here has to be deter- 

 mined by the characters discernible in a dorsal view. As in Thau- 

 mastoplax, the shape of the carapace is subrectangular with the 

 antero-lateral corners rounded off; the second ambulatory leg is 

 stronger than the first and third. Of the other Hexapodinae, or 

 Goneplacids Tvith only 3 pairs of walking legs, Hexapus de Haan 3 

 is more subcylindrical and has the three legs of subequal size; Larnb- 

 (lophaUus Alcock 4 has smaller orbits; Hexaplax Doflein 5 has very 

 oblique orbits seen from above, while Paeduma Rathbun 8 (=Amor- 

 phopus Bell 7 ) is said to be almost cylindrical. 



iAnn. Lye. Nat. Hist. New York, vol. 7, 1859, p. 60. 



fi Trans. Connecticut Acad. Sci., vol. 2, 1870, p. 168. 



3 Fauna Japon., 1833, p. 5 ; 1835, p. 35. 



±Journ. Asiat. Soc. Bengal, vol. 69, 1900, p. 329. 



5 Wiss. Brgeb. deutschen Tiefsee-Exped. Valdivia, 1898-99, vol. 6, 1904, p. 122. 



a Proc. Biol. Soc. Washington, vol. 11, 1897, p. 163. 



7 Jour. Linn. Soc. London, Zool., vol. 3, 1858, p. 27. 



