dlO 



ASIPHOSOPHORA.- 



-MOLLUSCA.- 



-ASIPHON'OPHOR*. 



■which fits into a pit in the surface of the other. The 

 family, as now restricted, is not numerous in species? 

 about a dozen only liaving been described. The genera 

 are il/yn, Sjihcenia, and Tugonia. 



Genus Mya. — This genus contains several species of 

 Bome utility. 



MYA AKENAEU (Plate 10, fig. 12), is used, both 

 in this country and in North America, as food for man 

 and as bait for fishes. On the banks of Newfoundland 

 the fishers bait their lines very successfully with it, and 

 it is said to be peculiarly acceptable to the cod. Dr. 

 Gould, in his account of the Invertebrata of Massachu- 

 setts, says, " The Clam {Mya arenaria) is still more 

 important in an economical point of view than the 

 oyster. It is extremely prolific ; and its exhaustless 

 banks are every day accessible during twelve of the 

 twenty-four hours." It is used for food, as well as for 



bait. About five thousand bushels of clams are annually 

 brought to market. Immense numbers are salted for 

 the bank fisheries — not less than five thousand barrels 

 every year. " Seven bushels of clams make about one 

 barrel of bait ; so that thirty or forty thousand bushels 

 are used in this prepared state, and perhaps as many 

 more are used from the shell. The value of the clam- 

 bait is six or seven dollars per barrel." — Gould, and 

 Juhnstun. 



MYA TEUNCATA is boiled and eaten by the in- 

 habitants of Zetland, where it is known by the nanio 

 of" Smurslin." In Greenland, according to 0. Fabii- 

 cius, these shells are much sought after by the walrus, 

 the arctic fox, and various Northern birds. 



Passing by the families of Corbulas {Corhulidw) and 

 Pandoras {Pandorida), we come to the second sub- 

 class :— 



Sub- CLASS II.— ASIPHONOPHORA. 



This sub-class is divided into three orders : — 



1. Lasiacea, in which the mantle lobes are imited, 

 with an anal siphonal aperture under the hinder 

 adductor muscle, and a large opening for the passage 

 of the foot. 



2. Unionacea, in which the mantle lobes are free, 

 slightly united behind, forming a separate and siphonal 

 opening placed under the hinder adductor muscle. 



3. Pectinacea, in which the mantles are free all 

 round, without any separate opening for the vent and 



i out-going current. 



Oeder I.— lasiacea. 



Family— SOLENOMYID^ 



In this family the shell is elongated, cylindrical, 

 obtuse at the extremities, and gaping. The valves are 

 clothed with a dark, horny, shining epidermis, which 

 extends beyond the margins. The hinge has a cardinal 

 tooth in each valve, and a callosity running between 

 them. The family consists of only one genus. 



Genus Solenomva. — This genus contains only four 

 known species. They are usually found burrowing 

 in mud, in about two fathoms water, but at the same 

 time are capable of leaping and swimming about with 



great freedom. Mr. Stimpson, an American concholo- 

 gist, has observed them making surprising leaps and 

 swimming about in the water for a considerable space 

 of time without touching the bottom. The leap appears 

 to be performed by the animal suddenly drawing in its 

 large umbrella-shaped foot, at the same time that water 

 is expelled from the hinder opening by the closing 

 of the valves. The genus is represented in Plate 11, 

 fig. 13, by Solenomya mediterranca. 



The families Laseidce and Montacutidm possess 

 no great interest; we will therefore pass on to the 

 second order ; — 



Order II.— UNIONACEA. 



Family— LUCINID^. 



The shells of this family are of a more or less orbi- 

 cular shape, free, and closed. The hinge varies very 

 much ; in most cases, however, there are one or two 

 cardinal teeth, and two lateral teeth in each valve, 

 though these are sometimes obsolete. Externally they 

 are variously sculptured, and internally they are always 

 dull and obliquely furrowed. The ligament is external 

 or subinfernal. The species are rather numerous ; they 

 are chiefly natives of temperate and tropical seas, living 

 upon sandy and muddy bottoms, and ranging from the 

 sea shore to great depths. A good many genera have 

 been formed, their characters being derived from the 

 structure of the hinge, the ligament, &o. These are 



Lucina, Loripe^, Corhis, and Ungulina. The family 

 is very well represented in Plate 11, fig. 14, by Corhis 

 fimhriata. 



Family— ASTARTID^. 



In this family the shells are free, of a solid substance, 

 oblong or cordate in shape, smooth or concentrically 

 ribbed on the external surface and covered with a thick 

 brown epidermis. The hinge is furnished with strong 

 teeth — two diverging cardinal teeth in one valve, and 

 one in the other. The ligament is exterual. Upwards 

 of fourteen species have been described; they are found 

 living in sandy mud, and are almost all found in the 

 Northern seas — ranging geographically from Welling- 



