EAST COAST MARINE SHELLS 



approached. Beyond the littoral region 

 light does not penetrate. 



The Archibenthal Region . Here the 

 various continents slope sharply to the 

 bottom of the sea and, there being no light, 

 there Is no vegetation. Dpon the upper 

 portions of this region, however, condi- 

 tions are peculiarly adapted to the develop- 

 ment of molluscan life. Ocean currents, 

 such as the Gulf Stream, bathe the animals 

 in clean warm water and also bring abundant 

 food to the organisms in their path. 



The Benthal or Abyssal Region . This 

 refers to the cold dark depths of the sea. 

 The animals there originated elsewhere but 

 have succeeded in adapting themselves to 

 the strange conditions. Thus many deep-sea 

 shells show affinity with those from shal- 

 low water. They are invariably colorless 

 and thin, due probably to the tranquility 

 of the water and absence of disturbances. 



The enormous pressure at these 

 depths, which may amount to several tons to 

 the square inch, necessitates the free per- 

 meation of water to all tissues in order 

 that equalization may result. How organ- 

 isms can function under these circumstances 

 is the greatest mystery of abyssal life. 



The collections made aboard the 

 U. S, Steamer Blake, over a period of years, 

 on the southeastern coast of the United 

 States show 28 per cent of the species ob- 

 tained from the abyssal fauna belong to 

 three families, namely TURRIDAE, NUCULANI- 

 DAE, and DENTALIIDAE. 



Littoral Zone Collecting 



Shore collecting is more or less 

 familiar to all. Llttorina, Thais, Acmaea, 

 and Chiton live upon rocks. Dpon sandy 

 beaches live many bivalves such as Donax, 

 Pecten, and Venus, while among the uni- 

 valves are Ollva, Olivella, and Busycon. In 

 sheltered bays upon mud flats exposed by 

 receding tides are countless Cerlthium and 

 Nassa. Where rocks, sand, and mud meet the 

 greatest number of species congregate, es- 

 pecially when there is an abundant food sup- 

 ply. 



Tides and winds should be carefully 

 studied and advantage taken of extreme low 

 tides which greatly facilitate collecting 

 expeditions. An offshore breeze, after a 

 protracted blow, often will furnish ideal 

 conditions. 



Almost every species has peculiar 

 preferments with respect to its place of 

 lodgment or attachment and it is almost use- 

 less to seek certain species except in spe- 

 cific places. Stones should be turned over; 

 sponges, grasses, old dead shells, wooden 

 piles and other surfaces carefully examined; 

 crevices peered into and all out-of-the-way 

 spots thoroughly scrutinized. 



Shells like limpets and Chitons 

 should be approached carefiilly and detached 

 with a small case knife before they become 

 alarmed. Otherwise it will be impossible 

 to dislodge them without injury to the 

 shell. It would be well to carry a few 

 small wide-mouthed glass jars in which may 

 be placed the medium-sized living forms. 

 After studying the movements of these in 

 salt water they may be preserved by cover- 

 ing with denatured alcohol. With a little 

 practice and experience the novice will 

 soon attain the necessary technique in ac- 

 quiring and caring for field specimens. 



Certain mollusks must be sought for 

 imbedded in the tissues of fish, starfish, 

 sea urchins, in the stomachs of fish, in 

 sponges, and upon the shells of other mol- 

 lusks. Certain of the parasitic shells are 

 singularly beautiful and not well known. 



Fossil Mollusks 



Often the collector has an oppor- 

 tunity to obtain fossil shells, especially 

 when washed out by heavy rains or when con- 

 struction of dikes or roads necessitate the 

 removal or uncovering of the soil. In many 

 parts of the south there are exposures of 

 fossil beds in river banks or bluffs. 



The shells from the most recent de- 

 posits are usually identical with or close- 

 ly related to those living on adjacent 

 coasts today. These and those of greater 

 antiquity are extremely valuable for com- 

 parison with the living species. The French, 

 in their museums, place recent and fossil 

 specimens side by side. 



The richest fossil beds in the 

 United States are adjacent to and upon the 

 banks of the Caloosahatchee River, Florida, 

 and belong to the Pliocene Period. These 

 shells are remarkable for their size, per- 

 fect preservation, and beauty. Recent con- 

 struction of dikes adjacent to Lake Okeecho- 

 bee, particularly near Clewiston, has made 

 available to students and collectors a very 



