408 MEMOIRS OF THE CAENEGIE MUSEUM 



are b3Mio means absent. There is some variability in this ehanieter. (lenerally 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 lareola is widest in specimens from 

 Fayette and eastern Greene (-ouuties. 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 ( 'ounty ; llice's Landing, (Ireene County). Such 

 specimens with punctures on the areola, which is accordingly wide, are scarcely 

 found anywhere else. I possess only one from rittsbui'gh. 



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 ai'e many speciniens 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. Howevei', it is actu- 

 ally not longer than in the eastern form. 



3. The swelling at the posterior ends of the pusinrliildl ri(l(jes is sometimes more 

 distinct in western specimens. 



4. In oni- western form the rjifriml nrJiiUi! (iin/lc is rarel}' angular, l)ut generally 

 blunt or rounded. In some cases it is very slightly developed. 



f). There are specimens in western Fennsylvania where the posterior section of 

 the telson is longer and more tapeiing. In extreme cases this is I'ather .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. Avtennal sciile in the western firm often slightly wider than in the eastern, 

 and with a stronger spine. This difference, however, is very slight. 



7. <'h(hr in the western form (PI. 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 in-egular, and merges into the scattered tubercles present 

 upon the inner half of the upjier surface. These latter tubercles are invariably 

 present, and are much more numerous than in the eastern form. The dactylopodite 



