246 GEO. H. HORN, M. D. 



robust and more dilated behind. The Middle States specimens are 

 oblong and nearly parallel. Those from the Hudson's Bay region 

 southward to Colorado and west to Washington Territory, are of 

 somewhat shorter form and more obtuse in front. These remarks 

 must be accepted in the most general sense as every manner of in- 

 termediate forms occurs. 



In his " RevieAv" Dr. LeConte has suggested a number of races 

 based on the general form of the specimens, but as these were founded 

 on one, or at most two specimens in each case, sometimes on a male 

 or again on a female, they must be considered of no more value than 

 as types of individual variation. 



One character, however, requires explanation. His second race 

 is based on a " male 'with the ungual tooth short" in contradistinc- 

 tion to the others in which the males have a " long tooth on the 

 claw." These distinctions are purely relative. In all cases where 

 the same brood is examined, the males have always a tooth slightly 

 shorter than the female, although the difference is never so marked 

 as in inicans, for example. 



After an examination of vast numbers of specimens from all parts 

 where it occurs certain differences have been observed in the ventral 

 characters of the male which seem to indicate three races. 



The most common form of the Middle States region, probably the 

 same as those seen by Froehlich have the male as follows : 



Race fusca. — Penultimate segment impressed along its posterior 

 border, in front of which is a feebly elevated, slightly arcuate, ob- 

 tuse ridge, the last ventral segment transversely impressed and with 

 a few small granules. 



Race . — Carina of penultimate ventral more elevated, 



more arcuate at middle, the edge of the carina slightly free, that is, 

 the segment is slightly excavated behind the carina so that the edge 

 of the carina is slightly overhanging, the last segment slightly con- 

 cave, nearly smooth. 



Race . — This is merely an exaggeration of the preceding, 



the edge being still more projecting. 



Specimens of these three forms may be readily selected, but there 

 is every intergrade. The greatest number of individual or geo- 

 graphical variations seems to occur in the form with the feebly ele- 

 vated carina on the penultimate ventral. The first well marked 

 geographical variety has been described as 



