BULLETIN 39, UNITED STATES NATIONAL MUSEUM. [22] 



species of Macoma, aud the mud-loving Ilyanassa are invariable mem- 

 bers of the fauna and wherever a sprinkling of wiry salt-water grasses 

 checks the motion of the water there one finds hosts of Astyris, Cerithi- 

 opsis, Triforis, Bittimn and small species of Odostomia and MangiUa. 

 A little further seaward where the water rarely leaves them are the 

 oysters, with their attendant Anomia, Crepidula and little gastropods, 

 not to mention the drills and other enemies varying with the latitude. 

 In the narrow ditches commonly cut in New England for the quicker 

 drainage of salt marshes as the tide recedes, Littorinella is often abun- 

 dant with Bittium upon the vegetation. In half submerged beds of 

 peat Petricola and Zvrphcea live in borings which they enlarge as they 

 grow, while the piles of old jetties or the softened wood of wrecks when 

 split open usually reveal the borings of Teredo, Xylotrya, and Martesia, 

 often containing the author of the damage. The canals of sponges, of 

 the brittle sort known as "bread sponges," often contain small gastro- 

 pods which take refuge there; and such sponges are common on the 

 oyster beds and in the pools on stony beaches just below low-water 

 mark, especially on our southern and southeastern shores. The crannies 

 of old weed- grown seawalls are a good collecting ground and in such 

 places and on iioats and old piling some minute species usuall}^ occur 

 which may be vainly sought elsewhere. 



In tropical regions the coral reefs, whose tops are usually accessible 

 at low water, have a rich and varied fauna of their own. The stems 

 aud aerial roots of the mangrove are favorite haunts of lAtorinidce, tree- 

 oysters, GeritJiidea, and the like, many of which remain for hours out of 

 the water. In the mud at their base Area, Saxicava and many others 

 are almost inextricably mixed with the tubes of Vermetus, Petaloconchus, 

 aud various worms. When the roots extend into clear water they are 

 a favorite haunt of the salt-water species of Neritina and of Nerita. Un- 

 der the overhang of rocks and the sides of bowlders which stand between 

 tide marks the amphibious Siplionaria and Gadinia may be found asso- 

 ciated with chitons and true limpets. Among the pebbles at low- water 

 mark may be found hosts of Turbinidcv, like Uvanilla and Pacliypoma, 

 TrocMdw, like Ghlorostoma and Liotia, the slipper limj)ets, the cup and 

 saucer limpets ( Grucibulum), Gapulus, and Amalthea. In gravelly places 

 occur myriads of GeritMum and Golumhella ; while the cones prefer 

 muddy places, the bivalves the sandy beaches, and the murices the 

 rocks and oyster beds. The catalogue might be almost indefinitely pro- 

 longed, but the above hints will be sufficient to start any intelhgent col- 

 lector on the right track, when after a little experience he will not need 

 more detailed suggestions. 



For ordinary beach collecting the collector, beside pill boxes aud 

 vials for frail or minute specimens, and a supply of alcohol in one or 

 two wide-moutlied bottles or screw-topped jars,will find a basket or bag 



