THE NAUTILUS. 
53 
Unios, Lewis’ types of Anodonta dejecta. The species was furnished 
by Dr. H. C. Yarrow, Surgeon and Naturalist of the Wheeler Ex¬ 
pedition, and was said to have come from the Arkansas or its tributa¬ 
ries, west of the 100th meridian. The lot consists of three broken 
valves, two of them forming a normal pair but very much distorted. 
I saw in a moment that the shell I named Anodonta mearnsiana 
in the Nautilus, Vol. VI, no. 12, p. 134 was the same, and my 
name will therefore have to be relegated to the synonymy. 
Lewis described his species in Field and Forest, Vol. 1, nos. 3 and 
4, page 26, and in Wheeler’s Report upon Geographical and Geo¬ 
logical Explorations and Surveys West of the One Hundredth Meri¬ 
dian, vol. V, Zoology, p. 952, 1875, but did not figure it. 
I am almost certain that the locality given by Dr. Yarrow is 
wrong, as the specimens collected by Dr. Mearns were from San 
Bernandino Ranch, Arizona, out of waters that drain into the 
Colorado River of the West. A very large number of specimens 
were sent, and there can be no doubt as to where they were found. 
It would indeed be a strange thing if this species was obtained 
from two places seven or eight hundred miles apart, in two distinct 
drainage areas. As the locality given for Lewis’ species is rather 
vague, and a large amount of the collections of the Wheeler Expe¬ 
dition were made on the Pacific slope it is quite probable that the 
types of A. dejecta came from the Colorado drainage basin. 
Washington, D. C., Aug. 1st, 1894. 
DESCRIPTIVE NOTICES OF NEW CHITONS, V. 
BY H. A. PILSBRY. 
Ischnochiton ptychius n. sp. 
Shell small, oval, moderately elevated, with fine and distinct 
though rather obtuse dorsal keel and slightly convex side-slopes; 
bright flesh-pink, with afew T white dots along the sutures, and creamy 
angular patches on the outer portions of the pleura of some valves, 
the girdle dull flesh-colored with indistinct whitish mottling in some 
places. 
Median valves short, the posterior outlines slightly concave, with 
the beaks but slightly indicated. Lateral areas slightly raised, each 
