88 A REVISION OF THE- ASTACID.E. 



from Red Bank, N. J., Dr. Jos. Leidy, labelled "A. affirm [Jhk L. R. Gibbes)." 

 Gibbes states that his own specimens came from Florida. They probably 

 belonged to some other species. Hagen states that Gibbes' s types of A . Bar- 

 torm in the Academy of Natural Sciences of Philadelphia are C. affirm, but 

 they are in fact C. placidus Hagen (Nos. 12G a , 126 c ).* 



Types, male and female, of Girard's C affirm, from Reading, Pa., collected 

 by Professor Baird, were communicated to Dr. Hagen by Dr. Sthnpson. The 

 male belonged to the second form ; the specimens were yonng, with only one 

 lateral thoracic spine. I have mj-self discovered in the collection of the 

 Smithsonian Institution four types (two males, two females) of Gambarus 

 Peak! Girard (Smithson. Cat. No. 2081), from the Potomac River, Washing- 

 ton. The largest is 4-i in. in length, the smallest 3| in. They are the 

 adult C. affirm Say. These are the only types of Girard's Cambari now in 

 existence, as far as I can discover. The rest were probably burned when 

 loaned to Sthnpson, in the great fire of Chicago. 



Color. — Upper surface greenish, mottled with darker green, especially 

 on the chelte ; tips of fingers orange, preceded by a dark green ring, 

 which runs along the outer border of the hand to the wrists ; abdominal 

 somites ornamented with interrupted transverse chestnut-colored double 

 bands. Under surface of a lighter hue. In recent alcoholic specimens the 

 bands of the abdomen turn bright blood-red. 



In some specimens the basal segment of the telson has three spines on 

 each side of its posterior margin. 



The centre of distribution of C. affirm appears to be the great rivers 

 which empty into the Delaware and Chesapeake Bays. 



According to Dr. C. C.Abbott (American Naturalist, VII. 80, 81), "Cam- 

 /•tints affirm is apparently the river species at Trenton, N. J. We have been 

 able to find it, as yet, only in the Delaware River, usually frequenting 

 the rocky bed, but also, in i'rwev numbers, on the mud-bottomed portions 

 of the river. They are usually found resting under Oat stones, well out 

 from the banks of the stream, where the water is of considerable depth. 

 Wherever the vegetation is dense we have failed to find them; nor have 

 we seen anything to indicate that it is a burrowing species." 



Since this was written, Dr. Abbott and myself have taken C. affirm in 

 great numbers from shallow ditches in the Delaware meadows near Trenton, 

 N. J., in company with C. Blandingii. 



See p. 114 



