RANDOM NOTES ON NATURAL HISTORY. 



9 



The Shell - Bearing Mollusca of Rhode 

 Island. 



[BY HORACE F. CARPENTER.] 



Chapter IV. 



Before entering into a detailed descrip- 

 tion of the species comprising this immense 

 class, representatives of which are found 

 everywhere, I wish to say a few words about 

 the peculiar situation of Rhode Island, and 

 to offer a few suggestions on collecting spe- 

 cimens. 



The surface of the earth is divided into 

 zoological provinces, or centres of distribu- 

 tion. The eastern coast of North America 

 comprises four of the marine zoological 

 provinces : The Arctic, the Canadian or 

 Boreal, the Atlantic, and the Caribbean. 

 The Arctic Province extends from the Polar 

 Sea, including Greenland and British 

 America, to Newfoundland ; the Boreal, 

 from Newfoundland to Cape Cod ; the At- 

 lantic, from Cape Cod to Florida ; and the 

 Caribbean includes the Gulf of Mexico, 

 Mexico and Central America, and the is- 

 lands of the West Indies. 



Rhode Island is situated nearthe extreme 

 end of the Atlantic Province. Consequent- 

 ly-, our fauna is limited in species and in 

 size, hundreds of shells being found on the 

 coasts of the Middle and Southern States 

 which are not found here. On the other 

 hand, we are near the junction of two dis- 

 tinct provinces, and as, in the distribution 

 of species, the zoological provinces lap over, 

 as we may term it, into each other, we have 

 in Rhode Island representatives of a portion 

 of the Boreal fauna, which, however, do not 

 extend much farther southward. 



Cape Cod forms a barrier to man}' species, 

 a large number of which, though found in 

 abundance on the northern shores of the 

 Cape, are never found on the southern side, 

 just as at Panama, the Atlantic and Pacific 

 species are unlike, though separated onl}' 

 by a few miles of land. For the above 

 reasons I have included among the species 

 liable to be found in Rhode Island, all those 

 which have been found in Massachusetts 

 south of Cape Cod, and those of the Con- 

 necticut and Long Island shores. 



The habits of the marine Mollusca differ 

 much from each other. Some species bury 

 themselves in mud ; others adhere closely to 



rocks ; some are found in sand, and others al- 

 wa3's on seaweed ; some bore for themselves 

 a home in the chalk cliffs, or other and more 

 ' solid stone ; others penetrate floating logs 

 j and timber ; while others, such as the Stili- 

 fer, are found as parasites on star-fish and 

 sea-urchins. In searching for the marine 

 shells, we are obliged to look for the differ- 

 ent species under different conditions and 

 ' circumstances, so that for convenience we 

 may divide the field of exploration into 

 four belts or zones, viz. : The Littoral, the 

 Laminarian, the Coralline, and the Deep 

 ; Sea Zones. 



j The Littoral Zone is the tract of shore 

 j lying between tide-marks, and the time for 

 collecting those species which inhabit this 

 j zone must be regulated by the hour of low 

 j tide. If we arrive at the shore when the 

 tide is ebbing, we first examine near high- 

 I water mark, the piles of seaweed thrown 

 \ up by the tide, and look for shell sand to 

 j carry home, where we can examine it at 

 leisure ; we then carefully explore the tidal 

 I pools, the mudd}' flats, and the sandy shore, 

 and the rocks left bare by the retreating tide ; 

 some species bury themselves in the sand 

 as soon as the}' are uncovered from the 

 water, and can onl}' be obtained by digging 

 to the depth of a foot or more IdcIow the 

 surface, while others conceal themselves in 

 i the crevices of rocks and under stones ; 

 [ finall}', we search at the moment of lowest 

 tide among the seaweed and stones at its 

 edge, and by the help of a good pair of rub- 

 j ber boots we wade out still farther into the 

 water for those species which live at the 

 I edge of the Laminarian Zone. Advantage 

 may also be taken at the time of full moon 

 to examine tracts of shore that are inacces- 

 sible at other times. 



The Laminarian Zone reaches from low 

 water mark to fifteen fathoms. In search- 

 ing for shells in this zone, we no longer 

 confine ourselves to a particular hour of the 

 da}' ; the work must be done in boats, and 

 j by means of the dredge. Here we have 

 I real labor to perform, not simply stooping 

 over to look for specimens as on shore, but 

 he who would succeed in dredging must 

 have not only perseverance and patience, 

 but a pair of strong ai-ms (for pulling in a 

 I loaded dredge from the bottom of the bay 

 j is no boy's play), to say nothing of a strong 

 1 stomach to be able to escape the mal de meVy 

 I the terror of landsmen. 



