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 Encyclopaedia Britannica, would 

 form a new order, Amyaria, fide Dall, from whom the above is 

 mainly compiled. 



317 Leda eaelata Hds 



Odd valves occasionally washed ashore, San Diego, Monterey, 

 Peru. 



318 Yoldia cooperi Gabb 



A single valve found on the ocean beach north of False bay. 



319 Area (Barbatia) gradata Sby 



Abundant under stones at low water. 



320 Cardita (Oarditamera) 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, pi 16, figs 

 5, 6, 1871. (Generic name preoccupied.) 



Milneria minima Dall, Am Naturalist, Sept., 1881, p 178. 



[This curious little member of the Carditidae 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 speci* 



