246 



Bulletin 39 



418 



the Canal Zone, so easil}^ obtained at the present time, were not 

 available, and the only fossil remains collected by the early trav- 

 vellers were generally in the form of poorly preserved casts. In 

 1856 there appeared in the Pacific Rail Road Reports, the de- 

 scription of an internal cast as Gratelupiaf mactropsis, together 

 with scarsely recognizable Tiirritella ^atitnensis and aJtilira. 



These specimens obtained by Mr. W. P. Blake from the 

 Isthmus are the first noticed from the fossiliferous rocks in 

 Panama and Central America. 



The Lirophora madropsis described by Conrad from an in- 

 ternal cast as Gratelupia f , is one of the most abundant fossils in 

 the Gatun beds of the Canal Zone, associated wath the small- 

 er and more finely sculptured >^^?/c»rj/w^ Brown and Pilsbry. L. 

 maciropsis is a species of variable size, but moderately convex, 

 longer posteriorly and usuall}^ with the basal margin more or 

 less arcuated about the posterior extremity. The sculpture con- 

 sists of irregular, more or less confluent concentric lamellae, 

 which are overrun by fine radial lines. These radial lines may 

 remain strong or become obsolete as usual with specimens from 

 the Canal Zone. A narrow foliaceous band is developed on each 

 side of the escutcheon and another about the anterior extremity 

 below the lunule. The Costa Rican examples are often very 

 much larger than those of the Canal Zone, the concentric lamel- 

 lae are finer and less confluent and with more persistent radial 

 lines. The following measurements will illustrate the range in 

 size : 



Length 30, heigth 23, thickness 15 mm, Central Zone. 

 37, 28, 19 



41.5, 32, 9.5 mm (right valve) 



Old Man Sam Creek, C. R. 

 51.5, 38, 21.5 mm, Sousi, C. R. 



Gatmi Stage: Gatun, and Mt. Hope, C. Z. 



Old Man Sam creek, C. R. 

 Sousi creek ( Upper Hone creek) 

 Banana River. 



