280 



LOWER INVERTEBRATES. 



Fig. 303. 



- Macoma sabitr- 

 losa. 



Fig. 304. — Macoma 

 /usca. 



this species can burrow beneath the sand, .and thence extend its long siphons to the 

 surface. In Macoma the thin white shell is covered with a dusky epidermis. M. 

 sabulosa is a more northern foi-m, extend- 

 ing as far south as Long Island Sound, while 

 the more common M. fusca reaches the 

 coast of Georgia. In muddy places this 

 latter species possesses but little beauty, 

 but when living in clean sand the epidermis 

 becomes thinner, and the shells frequently 

 have a delicate rose or lemon color. 

 Donax is an easily recognizable geims, in which the posterior end of the shell 

 appears as if cut off at a more or less oblique angle. The species occur in tropical 

 and semi-tropical regions, where they bury an inch or two beneath, the sandy shores. 

 Our two species, D. fossov and D. variabilis, occur abundantly in some places in the 

 southern states, the former reaching as far north as New Jersey and Long Island. 



Space will allow but a mere mention of the other prominent genera of this family; 

 Paphia, Semele, tScrobicuhiria, Pnatntitohia, Saiifjuinolaria, etc., which embrace many 

 beautiful forms, but onlj' few of which anything of popular interest can be said. 

 Scrobicularia piperata of the INIediterranean is occasionally eaten, and receives its 

 specific name from its pcjipcry taste. 



The jNIyid^e has an importance among the molluscs of the northern seas far out of 

 proportion to the number of species, for the long clam, or soft-shell clam, is its most 

 prominent member. In all the family the shell is thick and strong, and when closed 

 as far as possible, it still gapes at one or both ends. The hinge cartilage is internal, 

 and rests in a peculiar process of the left valve, as diagrammatically shown in Fig. 

 265, on a preceding jiage. The foot is small, the mantle margins have but a slight 

 pedal ga]ie, while the very extensible siphons are united their whole extent. 



J/y« arenaria, the clam par excellence, which figures so largely in the celebrated 

 New England clam-bake, is found in all the northern seas of the world, and is too 

 well known to need any technical description. All along the coasts of the Eastern 

 States, every sandy shore, every mud flat, is full of them, and from every village and 

 hamlet the clam-digger goes forth at low tide to dig these esculent bivalves. Tiie 

 clams live in deep burrows in the firm mud or sand, the shells sometimes being a foot 

 or fifteen inches beneath the surface. When the flats are covered with Avater, his 

 clamshii) extends his long siphons up through the burrow to tlie surface of the sand, 

 and through one of these tubes the water and its myriads of animalcules, is drawn 

 down into the shell, furnishing the gills with oxygen and the mouth with food, 

 and then the water, charged with carbonic acid and foecal refuse, is forced out of the 

 other siphon. When the tide ebbs, the siphons are closed and partly withdrawn. Tlie 

 clam begins its burrow at a very early stage, and keeps enlarging and deepening it as 

 it grows older. An old clam dug up and left on the sui-face has hard work to make a 

 new burrow. 



The white settlers were not the first to find out the i)alatable qualities of the clam, 

 the Indians knew it and loved it long ages before. On the shores of every promon- 

 tory and bay along the New Englajid coast are old shell heaps, ' kjokkenmoddings ' 

 the archaeologist calls them, which tell of many a feast by the red man. The careful 

 explorer, by raking them over, finds not only the shells of the common clam, but those 

 of many other molluscs, and bones of various animals as well, together with the tools 



