308 GEOLOGICAL SURVEY OF THE TERRITORIES. 
collected by Dr. Yarrow, Lieutenant Wheeler’s Survey west of the 100th 
Meridian. 
Zimapan, Mexico, (Prof. W. Dunker coll.), Claus. 
This species is exposed to considerable variation, so that I was mis- 
led by the rather indifferent figure of Baird in considering it as dis- 
tinct from H. caldwelli from Lake Winnepeg; and described it as #. 
clarkii. The-specimens from New Mexico are large and well developed, 
- little and a larger than in the majority of the 
Kansas specimens. They agree well with 
Claus’s figure of the shell, and the appendages 
are much as he figures them, so that as the 
species is abundant in New Mexico, I do not 
doubt but that it extends to Zimapan, Mexico, 
and thus the name for our most common and 
widely spread Estheria should be mexicana of 
Fis. 10.—Estheria mexicana, en- Claus. This species is allied to the Kuropean 
larged four times. #. dahalacensis, but the beak is fuller. 
I have ventured to place LH. dunkeri from Zimapan, Mexico, as a syno- 
nym of this species. Baird’s description is almost identical with that of 
his #. caldwelli; but my New Mexican specimens have the same out- 
line, the same number of lines of growth, and only differ in having less 
full and prominent beaks; but the artist may have exaggerated this 
feature in his drawing, though it is referred to in Baird’s description, 
yet some smaller Kansas specimens have fuller beaks than the New 
Mexican ones, but, as the locality (Zimapan) and collector (Dunker) 
are the same as Claus’s EH. mexicana, there is little doubt but that taking 
into account the tendency to variation in this species our synonymy is 
correct. 
ESTHERIA MORSEI Packard. 
Plate XXIV, fig. 7; XXVI, figs. 1, 2. 
Estheria morsei Packard, Amer. Journ. Sc., II, Aug. 1871. 
Sixth Report Peab. Acad. Sc. Salem, 56, June, 1874. 
Hayden’s U. 8S. Geol. Surv. Terr. for 1873, 619, 1874. 
Morse’s First Book of Zoology, 149, fig. 138, D. (No name.) 
Shell much fuller, more globose than in any of the preceding species, 
with fuller, more prominent, less oblique, and centrally situated beaks; 
shell oblong oyal, of a pale horn or amber color. Dorsal edge shorter 
than in H. mexicana, and in front of the beaks, instead of being straight 
and suddenly curved downward, is regularly rounder, much as in WH. 
belfraget ; posteriorly the dorsal edge slopes rapidly downward, without 
the well marked angle of H. mexicana. Coarse punctures between the 
lines of growth, rather coarser than in I. mexicana, there being on an 
average 5-10 of these marking between the ribs in the center of the 
valve. Plate XXIV, fig. 7, also represents the markings at the edge of 
the shell. 
Second antenne, with a larger scape than in Z. belfragei, 17 joints in 
the upper, 16 in the lower, flagellum. Legs of the male with a smaller 
lower division of the flagellum, and a smaller gill than in WL. belfragei, 
while the upper division or oviger is much shorter and broader than in 
any of the foregoing species, being no longer than the gill. The hand 
is apparently a little thicker than in LH. bel/ragei. 
Telson much as in H. mexicana, with about 20 pairs of teeth, coarser 
than in JL. belfragei, about 5 pairs of which are much larger than the 
others. . 
Length, 12.2™™; height, 8.2™™; thickness, 6™™. 
