46 THE - 
CONCHOLOGISTS’ 
EXCHANGE. 
THE SHELL-BEARING MOLLUSCA OF 
RHODE ISLAND. 
* 
BY HORACE F. CARPENTER. 
meet 18 
Genus Meesnicra Conrad—1867. 
“Conrad’s Catalogue of the Family Solen- 
idze”’ gives but three species of the genus Meso- 
pleura, one of which inhabits Java, one Cali- 
fornia, and the other the Atlantic Coast of the 
United States: this is 
Mesopleura centraiis, Say. 
Shell small and delicate, transversely oblong- 
oval; surface smooth in the centre and wrinkled 
concentrically at each end; a reddish stripe or 
band passes from the umbones across the 
valves, which can be seen through the shell 
from the inside; epidermis pale yellowish; in- 
terior smooth and shining; hinge teeth nearly 
central, Length, one anda half. inches; height, 
one-half inch: breadth, seven-twentieths. 
This species is of southern distribution, and 
is never found north of Cape Cod. ‘There is a 
difference of opinion among Conchologists 
whether or not this species is identical with the 
European Solen divisus, Spengler, 1794. If 
they are the same, its name should be that of 
Spengler, a shell with several synonyms, such 
as, fragilis, Pult, 1799; bidens, Chemn, 1795 ; 
divesa, Gray, &c., &c. Our species was de- 
scribed by Say in Journ. Acad. Nat. Science, 
Phila., 11: ya6, 1822. 
Gould says, “ It.is occasionally found at New 
Bedford and other places in Buzzards Bay. It 
is rather common about Rhode Island.’ I 
“have never been able to find a single specimen 
or even a piece of a valve in this State. Per- 
haps he meant the Is!and of Rhode Island, 
and as I have not examined the eastern shore 
of Middletown, opposite Little Compton and 
Tiverton, I give him the benefit of the doubt. 
FAMILY SAXICAVID. 
gaping at both ex 
hinge with one cardinal tooth; liga- 
Shell equivalve, thick, 
tremities ; 
ment external, prominent, solid. Siphons of 
the animal, large, elongated, covered with a 
thick skin, the orifices fringed. There are 
three genera with about thirty species. 
Genus Saxicava, Fleurian de Bellevue, 1802. 
Shell, when young, with two minute teeth in 
each valve; toothless when adult. 
The Saxicavids are found in crevices of 
rocks and roots of sea weed, moored by a byssus 
of threads spun by the foot of the animal Also 
found on oysters, adhering to the irregularities 
of the surface. ‘They also bore like the Pholas 
into clay, peat and even into limestone, but 
more frequently occupy a habitation previously 
excavated by some other species. 
748.— Saxicava rugosa, Linn, 1767. 
4 5 ) ) 
Syns: 
Mytilus rugosus, Linn. Mya arctica, Linn, 
Shell oblong-oval, rough, irregular in shape, 
white, inequivalve -and inequilateral, gaping ; 
the posterior end sometimes rounded and some- 
times truncated ; epidermis dingy yellow, thin; 
beaks prominent, from which two ridges ran 
along the posterior slope, one near the margin, 
and the other to the lower angle; in some 
specimens these ridges are armed with spines ; 
valves generally toothless, but sometimes with 
a rudimentary tooth in one valve and a corre- 
sponding pit in the other. Length, one inch; 
height, three-fifths; breadth, two-fifths. 
No description of this species can be given 
that is not liable to mislead. It is more varia- 
ble in shape than any other shell known, and 
a list of its synonymy would be discouraging 
to a novice; fifteen or more species, placed in 
five different genera, and even put in different 
families, have been made from varieties of this 
species. 
Binney thinks there are two species in New 
England, rugosa and arctica, the latter a north- 
ern species, inhabiting Europe as well as Amer- 
ica. Tryon, on the other hand, includes both 
species under Saxicava arctica. Linnzeus also de- 
scribed in 1767. . Habitat, Atlantic and Pacific 
Coasts of NortlggAmerica; northern coasts of 
Europe to the M@diterranean. “Common from 
Mass. Bay to Labrador, from low water mark 
