EAST COAST MARINE SHELLS 



The term CONCHOLOGY Is derived from 

 a combination of two Greek words "A Shell 

 Fish" and "Science of." It is usually ap- 

 plied to the study of both animal and 

 shell. Another word, MALACOLOGY has Deen 

 accepted by many societies and individuals 

 to supersede the earlier one and refers 

 also to the study of the entire organism. 



The MOLLUSCAN PHYLUM comprises 

 those animals with soft fleshy bodies cov- 

 ered by a muscular sac, commonly called the 

 mantle, and which usually secretes a shell 

 composed of carbonate of lime which in 

 turn affords protection to the vital organs 

 of the body. 



POSITION OF THE MOLLUSCA. Cr. Rob- 

 ert W. Hegner in "College Zoology" places 

 the Phyla of the Mollusca between the An- 

 nelida (a group to which belong the jointed 

 worms) and the Arthropoda (which includes 

 the crabs, insects, etc.). The three share 

 one character in common, they are, or orig- 

 inally were, mostly bilaterally symmetrical 

 organisms. 



DIVISIONS or THE MOLLUSCA. There 

 are five great classes indicated by the 

 variations of the foot or locomotive organ 

 and named: CEPHALOPODA, GASTROPODA, SCA- 

 PHOPODA, PELECYPODA, ^nd AMPHINEURA. 



cephalopoda! or CEPHALOPODS. Ani- 

 mal with foot lacking or rudimentary, pos- 

 sibly modified to arms of which there are 

 eight to ten; individual, unisexual; ani- 

 mal free, crawling or swimming in the sea, 

 propelled by water from the slphcnal tube. 

 Examples: Octopus or Devil Fish, Nautilus, 

 Loligo or Squid. 



GASTROPODA^ or GASTROPODS. Dis- 

 tinguished by the presence of a sole-like 

 locomotive foot underneath. By its wave- 

 like expansions and contractions the animal 

 progresses. The well-known term UNIVALVE 

 refers to 'the one piece shell. Examples: 

 Helix (snail); Littorlna (periwinkle); Buc- 

 clnum (whelk) . 



Originally bilaterally symmetrical 

 organisms the Influence of environment has 

 often resulted in radical readjustments of 

 internal organs with consequent modifica- 

 tions in the shell. 



PELECYPODA^ or BIVALVES. Entirely 

 aquatic and predominately marine forms. The 

 term bivalve indicates a two-piece shell. 

 LAMELLIBRANCHIATA, which is also frequent- 

 ly applied to this group, refers to the 

 lamellar or leaf -like character of their 

 branchial gills. The tongue-like foot used 

 for ploughing through mud or sand is char- 

 acteristic, also the elastic ligament which 

 binds the valves together, and the inter- 

 locking teeth or denticles at the hinge. 

 Examples: oyster, scallop, and clam. 



SCAPHOPODA^ or TUSK SHELLS. Animal 

 with long filaments appearing from lobes 

 about the neck and enveloped, with the head, 

 by the mantle. Shell tubular, not spiral. 

 Example: Dentalium (Elephant's Tusk Shell). 



AMPHINEURA.^ Sometimes placed un- 

 der the Gastropoda. The Chitons or coat- 

 of-mail shells are externally bilaterally 

 symmetrical. They usually are provided 

 "vith a shell of eight transverse calcare- 

 ous plates. 



SUMMARY. A superficial examina- 

 tion reveals little in common to the pre- 

 ceding classes. However, there are several 

 structures shared by all, notably the foot. 

 With this organ the snail creeps, the clam 

 and tusk shell dig, the squid seizes its 

 prey. Also in each is a space known as the 

 mantle cavity, between the main body and 

 the mantle or enclosing envelope. This 

 mantle is peculiar to the Mollusca, as is 

 also the Radula which Is used for the rasp- 

 ing of food and as a tool for boring into 

 other shells. 



DEVELOPMENT. In the development of 

 the molluscan egg there is the TROCHOPHORE 

 stage. Fig. 1, which in turn becomes a 

 VELIGER LARVA (so named because of a band 



1. Gr. kephale , head; pous , foot. 



2. Gr. gaster, the belly; pous , foot. 

 5. Gr. pelekos , hatchet; pous, foot. 



4. Gr. skaphe , a boot; poua , foot. 



5. Gr. amphi , on both sides; neuron , nerve. 



