NO. 2 PYRAMIDELLID MOLLUSKS — BARTSCH 3 



numbers and in more perfect condition by excavation and screening. The upper 

 two feet is predominantly sandy, grading down into fairly pure marl below, 

 but penetration by means of hand-dug pits could not be carried deeper than a 

 few feet because of water encroachment. As reported by Mr. Locklin, some of 

 the pits in the marginal zone encountered black silty mud below the fossil zone, 

 closely resembling the recent swamp mucks of the vicinity. Because of its 

 unusual setting and relatively small size, the nature of the St. Petersburg fossil 

 formation was very baffling, and it could not be determined at once whether 

 it represented a natural outcrop or merely a secondary reworked deposit. In- 

 vestigations carried out largely by Mr. Fargo and Mr. Locklin, after the main 

 part of this paper had been prepared, show conclusively that this fossil band is 

 not a true bed, but fill and ballast material dredged or pumped from nearby pits 

 during the land-boom days of the 1920's. As these pits, now filled with water, 

 are relatively shallow, none exceeding 15 feet in depth, the Caloosahatchee 

 marls must lie fairly close to the surface over a considerable area in North St. 

 Petersburg and in the adjoining sections of Pinellas County. These Pliocene 

 shells have generally a distinctive buff or pale reddish color which easily dis- 

 tinguishes them from stray Recent or Pleistocene forms which are white or 

 cream-colored. Large shells are absent or represented by fragments, as these 

 could pass through the pump and pipe lines easily. However, the smaller shells 

 are often in an exquisite state of preservation and by their abtmdance show the 

 extreme richness of the Caloosahatchee marls at this place. . . . 



For a period of about ten years Mr. Fargo and Mr. Locklin have continued 

 to collect fossils from this locality. Many tons of marl or sand were washed, 

 screened and sorted, special attention being given to the smaller forms. Screens 

 of 20-30 mesh were used to save the small species. 



When one review^s the Pyramidellidae of that monumental work 

 by Dr. WilHam H. Dall entitled "Contributions to the Tertiary Fauna 

 of Florida and the Pliocene Beds of the Caloosahatchee River" 

 (Trans. Wagner Free Inst. Sci., vol, 3, pt. 2, 1892) one is astonished 

 at the change of concept expressed there and in the present paper. 

 These differences in interpretation are in reality an exposition of the 

 advancement in sciences and technology that have taken place in the 

 interval. When Dr. Dall produced that fundamental study our 

 knov^ledge of the distribution of geological formations was quite 

 limited and the collections from the various strata equally scanty. 

 The underlying oceanographic principles, such as ocean currents, 

 salinity, temperature, hydrogen-ion concentration, had scarcely been 

 touched upon. These are the factors that determine the zoogeographic 

 distribution of marine organisms, the boundaries of the territory 

 occupied by various species. They are the foundation stones upon 

 which the modern marine biologist bases his taxonomic studies. 



Then we must also remember that science in 1892 had not yet 

 produced the stereobinocular microscope and the useful incandescent 

 illuminating devices by which we can greatly enlarge the image of a 

 small object and hold it in steady focus and compare it side by side 



