﻿GEOLOGY AND PALEONTOLOGY OF THE CANAL ZONE. 131 



DESCRIPTIONS OF SPECIES. 



Subclass MALACOSTRACA. 



Order DECAPODA. 



Suborder NATANTIA. 



Family, genus, and species indeterminable. 



Plate 57, fig. 1. 



Locality. — Panama Canal Zone. Top part of limy sandstone below 

 upper conglomerate, near foot of i-tairs, Gaillard Cut. Upper part 

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

 T. W. Vaughan. collectors. 1011. Station 6012c. Cat. No. 324267, 

 U.S.N.M. 



Material. — One specimen slio^virlg three segments from the pleon 

 of a shrimp. Pleon compressed laterally. Each of the two overlap- 

 ping segments has the posterior angle produced backr^'ard in a 

 rounded lobe of moderate size. 



Family PALAEMONIDAE. 



MACROBRACHIUM, species, 



Plate 57, flgs. 4 and 5. 



Zo<?«?i?^y.— Panama Canal Zone. Las Cascadas section, Gaillard 

 Cut. From fifth or topmost limestone. Emperador limestone. Oli- 

 gocene series. D. F. MacDonald and T. W. Vaughan, collectors, 

 1911. Station 6019^. Cat. No. 324256, U.S.N.M. 



Material. — One i^ropodus of left cheliped, minus finger. Slightly 

 compressed, subcylindrical. Some of the outer crust is lacking, but 

 in general, the segment widens rapidly for the proximal two-fifths, 

 then widens gradually at the middle, but not at all in the distal two- 

 fifths. There is no shallow sinus in the lower margin behind the 

 finger, as in M. jamnicense,'^ M. acanthwus panamense ^ and others ; 

 neither is the palm like that of M. mexicanum^^ which is not at all 

 convex below, and has subparallel margins. 



The specimen resembles Macrohrackium more than it does any 

 marine genus now existing in Panamian waters. 



^Cancer (Astacus) jamaicensis Herbst, Natur. Krabbon u. Krebse, vol. 2, 1792. p. 57, 

 pi. 27, fig. 2. 



2Rathbun, in Smithson. Misc. Coll., vol. 59, No. 13, 1912, p. 1. 



^ Palaemon mexicanus Saussiire, M^m. Soc. Phys. Hist. Nat. Geu&ve, vol. 14, lcS5S, 

 p. 468 [52], pi. 4, figs. 27, 27o. 



