29 
its anterior extremity; about one-third from anterior end the 
mantle is perforated by an orifice, which pierces it in the vicinity 
of the mouth. The edges of this orifice project from the general 
surface, lined with close-set small papillae. At about the same 
distance from the posterior end is another tubular perforation, 
holding a similar relation to the anus; which has, however, plain 
edges, and is not internally papillose. Beneath the anterior 
trough of the mantle prolonged backward, like a slit with plain 
edges, to about the posterior third; from this projects a narrow, 
hatchet-shaped foot, with a strongly marked byssus-gland at its 
posterior angle; from this a bunch of white byssus extends to the 
stone or object to which this mollusk attaches itself. The cavity 
of the mantle extends some distance behind the commissure of 
the pedal opening. The anterior point of the foot is roofed by 
the trough-like expansion above mentioned. The mouth is pro- 
vided with 2 pairs of small palpi. Two gills very finely micro- 
scopically laminate, extend backward from near the mouth, on 
each side, to the posterior end of the body, the wider one being the 
inner; between their posterior ends a thin recticularly perforate 
veil connects the two pairs, and shuts off the anal area from the 
rest of the mantle cavity. The intestine contains a hyaline stylet, 
and is considerably convoluted; but the viscera offer no marked 
peculiarities when compared with ordinary pelecypods. The shells 
are enclosed in two little sacs in the substance of the mantle. 
The umbones are near together, apparently connected by a brown 
gristle resembling an abortive ligament, and are nearly over the 
heart. The valves are about 10 mm long, 1 wide, destitute of 
epidermis, prismatic, or pearly layers. There are no muscular or 
pallial impressions, no adductors, hinge, or teeth. They resemble 
in form the exterior of Gervillia, as figured by Woodward, and 
are pure white. As they lie in the body, they diverge at a rather 
wide angle from the beaks forward. The embryonic valves are 
retained like 2 tiny bubbles on the umbones. The animal forms 
the type of a new family, Chlamydoconchae, and under the classi- 
fication in the new edition of the Encyc!opaedia Britannica, would 
form a new order, Amyaria, fide Dall, from whom the above is 
mainly compiled. 
317 Leda celata Hds 
Odd valves occasionally washed ashore, San Diego, Monterey, 
eru. 
318 Yoldia cooperi Gabb 
A single valve found on the ocean beach north of False bay. 
319 Arca (Barbatia) gradata Sby 
Abundant under stones at low water. 
320 Cardita (Carditamera) subquadrata Cpr 
Queen Charlotte Islands, in 20 fms.—Todos Santos bay, Baja 
Cal. 
Shell small, solid, subquadrate, speckled with brown; soft 
parts yellow, with brown spots on mantle edge. 
321 Milneria minima Dall 
Ceropsis minima Dall, Am Journ Conch, vii, p 152, pl 16, figs 
5, 6, 1871. (Generic name preoccupied. ) 
Milneria minima Dall, Am Naturalist, Sept., 1881, p 178. 
[This curious little member of the Carditide was discovered 
in 1866 by the writer and found nestling on the backs of Haliotis, 
which afford a shelter for many small mollusks. The first specie 
