408 MEMOIRS OF THE CARNEGIE MUSEUM 
are by no means absent. There is some variability in this character. Generally a 
very narrow space is left between the two lines, which does not leave room for any 
punctures. But it is a curious fact that the jareola is widest in specimens from 
Fayette and eastern Greene Counties. In these localities specimens with an entirely 
obliterated areola are exceedingly rare, and specimens with the areola so wide that 
there is room for one irregular row of punctures are rather frequent, (Pennsville, 
Dunbar, Smithfield, Fayette County; Rice’s Landing, Greene County). Such 
specimens with punctures on the areola, which is accordingly wide, are scarcely 
found anywhere else. I possess only one from Pittsburgh. 
2. Rostrum, in all eastern specimens at hand, with a more or less distinct acu- 
men. In the western form there is a distinct tendency to render the acumen ob- 
scure. Indeed there are many specimens which have the acumen exactly as in the 
eastern form, but there are as many where it is not marked, the margins converging 
evenly to the tip. In such specimens the rostrum assumes a rather regular lanceo- 
late shape, and appears somewhat more elongate and narrow. However, it is actu- 
ally not longer than in the eastern form. 
3. The swelling at the posterior ends of the postorbital ridges is sometimes more 
distinct in western specimens. 
4. In our western form the external orbital angle is rarely angular, but generally 
blunt or rounded. In some cases it is very slightly developed. 
5. There are specimens in western Pennsylvania where the posterior section of 
the telson is longer and more tapering. In extreme cases this is rather striking, the 
posterior section being distinctly longer than the anterior, and longer than wide. 
This latter condition is never found in eastern specimens. On the other hand there 
are many western specimens which do not differ in this respect from the eastern, 
and many transitional conditions have been observed. 
6. Antennal scale in the western form often slightly wider than in the eastern, 
and with a stronger spine. This difference, however, is very slight. 
7. Chelz in the western form (Pl. XL, Fig. 7) of slightly different shape, but this 
difference always holds good, provided the chela has not been regenerated, and is 
otherwise normally developed. The inner margin of the palm in the eastern form 
has always two rows of tubercles, while on the upper surface there are at the best 
only a few minute, scattered tubercles, chiefly near the base of the dactylopodite. 
In the western form the two rows of tubercles are also generally distinguishable, 
but often the inner row is irregular, and merges into the scattered tubercles present 
upon the inner half of the upper surface. These latter tubercles are invariably 
present, and are much more numerous than in the eastern form. . The dactylopodite 
