GEOLOGY AND PALEONTOLOGY OF THE CANAL ZONE. 175 



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

 and T. W. Vaughan, collectors. 1911. Station 6012<?. 



Holotype.C&t. No. 324226, TJ.S.N.M. 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 HEXAPODESFAE. 



Living representatives of this subfamily are restricted to the Indo- 

 Pacific region. 



Genus THAUMASTOPLAX Miers. 



Tliaumastoplax MIERS, Ann. Mag. Nat Hist, ser. o. vol. 8, 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 with only 3 pairs of walking legs, Hexapus de Haan* 

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

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

 oblique orbits seen from above, while Paeduma Eathbun 6 (Amor- 

 Bell 7 ) is said to be almost cylindrical. 



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



- Trans. Connecticut Acad. Sci., vol. 2, 1870, p. 163. 

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

 *Journ. Asiat. Soc. Bengal, TO!. 69, 1900, p. 329. 



* Wiss. Ergeb. deutschen Tiefsee-Exped. Valdivia, 1898-99, vol. 6, 1904, p. 122. 

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



7 Jonr. Linn. Soc. London, ZooL, vol. 3. 1858, p. 27. 



