16 ASTACID^. 



Hands. — The hands, or great claws, are, in every description, care- 

 fully used as one of the best specific characters. No doubt their form 

 and sculpture are quite different in many species, and offer characters 

 most easy of recognition. Nevertheless, these characters become more 

 and more uncertain as the materials in hand are richer. As I have 

 stated before, the development, the size, and the sculpture of the hands 

 vary considerably between the first and second form males and the 

 females, between the young, middle-aged, fall-grown, and gigantic speci- 

 mens. Even the relative length and breadth differ ; the brachium sur- 

 passes the eyes or not ; the fingers are equal or unequal in length, 

 longer than the rest of the hand or not, straight or curved, denticulated 

 at the margins or not ; the carpus has the spines more or less numerous, 

 more or less developed. In the full-grown specimens the hands are 

 surely a constant and good specific character, but even here they vary 

 to a certain degree, and finally it is not at all easy, with scanty mate- 

 rials, to determine with certainty whether a specimen be full grown or 

 not. Therefore I have never given in the different species the exact 

 and detailed measurements of these parts, which are noted by some 

 authors, as I have found these measurements of very little value. The 

 measurements given by me are average measurements, generally of the 

 most full-grown specimens. But I have always been careful to record 

 all the different forms of the hands which I have observed in each 

 species. 



The hairyness of the hands, which, like a beard, a brush, or a pencil, 

 is found in some species (A. Gambclii, 0. penicillatus immunis, etc.), 

 seems constant and a very good specific character ; the same is true of 

 the partial hairyness on the first pair of maxillary legs (outside and 

 below, or outside only). 



On the basal joint of the fourth and of the fifth pair of legs there 

 occurs a little knob (capitulum), differing in its shape in given species 

 in a constant manner. 



Colors. — The colors are apparently of no value. I have not seen liv- 

 ing specimens, but Dr. John Le Conte says directly : " All that I have 

 ever seen were much of the same color," and " their color is generally 

 lost with their life, so that it is of little value in the description." All 

 the alcoholic specimens have a similar color, — reddish brown, inclining 

 to a more or less dark olive or dirty yellow. In certain species red 

 spots are occasionally to be found in some species, as noticed in my 

 descriptions. I should remark that the color is apparently altered in 

 alcohol as time advances. The specimens of C. Bartonii received with- 

 in a few weeks are reddish brown, the older ones nearly yellow. 



Dr. John Le Conte says expressly that the burrowing species do not 

 differ from those that are aquatic. 



