SCKOBICULAKIA.- 



-MOLLUSCA.- 



-Glossus. 



303 



rival's of Western Africa, as high as twenty miles from 

 the sea. 



Genus Scrobicui.aria. — This genus, forming the 

 tyiie of a small family Scruhiculariida;, has an oval, 

 thin, compressed shell, and the cartilage is internal, and 

 eituated ia a shallow, triangular pit. The species of 

 tihell upon which the genus is founded, is a native of 

 our own shores, and is found living buried vertically 

 live or six inches deep. The most remarkable circum- 

 stance iu the history of this shell, perhaps, is the num- 

 ber of names by which it has been described. 



Family— MACTRID^. 



The Mactras have an equivalve, trigonal shell, which 

 in some is close and in others slightly gaping, and in all, 

 covered with a thick epidermis. Tlie hinge is furnished 

 with two diverging cardinal teeth in each valve, the 

 central one being laminar and folded, and usually with 

 an anterior and postf^rior lateral tooth, those of left 

 valve being single, and those of right double. The 

 cartilage is internal, and is jilaced in a deep triangular 

 pit behind the cardinal teeth. The pallial sinus is 

 short and rounded. 



The true Mactras {Maclrinai) have a more or 

 loss trigonal shell, nearly closed behind. The anterior 

 hinge tooth is bifid or triangular, and the lateral teeth 

 are distinct, well developed, and laminar. They inhabit 

 sandy coasts at various depths, though the majority, and 

 especially the larger kinds, are littoral. The animals 

 are active and powerful for their size, and live buried 

 in the sand at a small depth beneath its surface. " The 

 foot can be stretched out considerably, and moved about 

 like a finger; it is also used for leaping." — ( Woodward.) 

 The British species afford food to the star-fishes and 

 whelks, and Mr. Alder informs us that one species, 

 Maclra siihtruncata, a common one in the island of 

 Arran, is collected by the natives to feed their pigs 

 with. There are several genera in the Muctrinie, 

 oliaracterized chiefly by the position of the ligament. 

 These genera are Mactra, Schisodimiia, S^iisula, Muli- 

 nin, and Gnathodon. The family is represented in 

 Plate 10, fig. 3, by a British species, 3/ac<ra atultorum. 



Genus Gnathodon. — This genus has an oval, ven- 

 tricose, thick and smooth shell, with eroded beaks and 

 an olive epidermis. The hinge is furnished with two 

 cardinal teeth in one valve, and one in the other, and 

 the lateral teeth are doubled in the right valve, elon • 

 gated and striated transversely. The ligament is 

 internal and placed iu the upper edge of the deep, cen- 

 tr.d cartilage pit. 



GNATHODON CUNEATUS— perhaps the only species 

 of the genus — is a native of New Orleans, and was 

 formerly eaten by the Indians. It lives in vast num- 

 bers in the extensive flats below Mobile, burrowing 

 three or four inches beneath the surface of the sand, in 

 which numerous depressions indicate where they are 

 to be found. The water there is only brackish, though 

 there is a tide of three feet. Banks of dead shells, three 

 or four feet thick, are found twenty miles inland, and 

 Mobile is built on one of these banks. " A deposit 

 composed entirely of two existing shells in a subfossil 

 state, the Cyrena Carolinensis, and more especially the 



Rtiiifjia cyrenoides of Des Moulins {^Giialhodon 

 ctiiiedtus), extends along the whole shore of the Gulf 

 of Mexico from Pensacola to Franklin in Louisiana, 

 bends round Mobile bay. Lake Pontchartrain, and 

 ranges across the delta of the Mississippi immediately 

 above its marshes, a total distance of nearly three hun- 

 dred miles, and probably ranch further ! It is remark- 

 able that the shells occur in beds with scarcely any 

 admixture of sand or earth, and they are consequently 

 found extremely useful in repairing roads and paving 

 the streets of the city. They are dug from the surface 

 of the soil, both on the main shore and the islands of 

 the bay. These deposits border the bays of the Gulf 

 of Mexico, between Mobile and New Orleans, and they 

 occur in the vicinity of Franklin, Louisiana. The 

 Ohandcleur Isles, between Mobile bay and the delta of 

 the Mississippi, consist of deposits of these shells covered 

 by a fertile soil." {Johnston — Report of British Associa- 

 tion.) The road from New Orleans to Lake Pontchar- 

 train (six miles) is made of Gnathodon shells procured 

 from the east end of the lake, where there is a mound 

 of them a mile long, fifteen feet high, and twenty to 

 sixty yards wide. In some places it is twenty feet above 

 the level of the lake. — [Lyrll, in Woodward.) 



The Lutrarias or " Otter shells" {Liilrariince) 

 have oblong or elongate shells, gnping at both ends 

 and covered with an epidermis. The plate on which 

 the cartilage is fixed is prominent, and has one or two 

 small teeth iu front of it in each valve. The lateral 

 teeth are very small, rudimentary, often obsolete. The 

 pallial sinus is deep, horizontal. The Otter shells are 

 found in various parts of the world. They live habi- 

 tually buried in the mud, fixed in a vertical position, 

 and are principally met with in estuaries, at dei)ll]s 

 varying from low water to twenty fathoms. Several 

 genera have been found in this group. 



Family— PAPHIID^. 



This family, composed of the genera, Paphia, Meso- 

 desma, DonaciUa, and Ana2)a,\iave an equivalve, closed 

 shell, with the cartilage in an internal pit, and with a 

 simple compressed cardinal tooth and a rudimentary 

 process in the place of the second tooth. The form of 

 the shell is various. The Paphias are ovate, somewhat 

 trigonal, truncated behind, and slightly keeled. The 

 Mcsodcsinas are transversely ovate shells, with the hinge 

 in the miildle. The Donacilhe are wedge-shaped shells, 

 with the hinge at one end. These shells live in sands 

 in New Zealand and other parts of the world, and some- 

 times are found in estuaries. 



Genus Glossus (;=/«oc((;-rf«(), the "Heart Cockle." 

 — This genus, forming the type of a small (iimily, 

 Glossidat, has a peculiar heart-sliaped shell, whence its 

 English name. It is ventricoso, equivalve, smooth or 

 fuiTowed externally, with prominent contorted beaks, 

 and a hinge consisting of two very oblique cardinal and 

 two lateral teeth in each valve, the anterior being some- 

 times obsolete. The ligament is external, and there is 

 no pallial sinus. Mr. Bulwer, who had an opportunity 

 of watching our British species, Glossus cor, alive, 

 tells us that on being placed in a vessel of sea-water, the 

 valves of the shell gradually opened; the feelers or 



