GEOLOGY AND PALEONTOLOGY OF THE CANAL ZONE. 131 



DESCRIPTIONS OF SPECIES. 



Subclass MALACOSTRACA. 



Order DEGAPODA. 

 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 stairs, Gaillard Cut. Upper part 

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

 T. W. Vaughan, collectors. 1911. Station 6012c. Cat. No. 324267, 

 U.S.N.M. 



Material. — One specimen showing three segments from the pleon 

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

 ping segments has the posterior angle produced backward in a 

 rounded lobe of moderate size. 



Family PALAEMONIDAE. 



MACROBRACHIUM, species. 



Plate 57, figs. 4 and 5. 



Locality. — Panama Canal Zone. Las Cascadas section, Gaillard 

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

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

 1911. Station 6019#. Cat, No. 321256, U.S.N.M. 



Material. — One propodus 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. jamaicense, 1 M. acanthurus panamense 2 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 M acroorachiv/ni more than it does any 

 marine genus now existing in Panamian waters. 



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

 pi. 27, fig. 2. 



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



3 Palaemon mcxicanus Saussure, Mem. Soc. Phys. Hist. Nat. Geneve, vol. 14, 1858, 

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



