26 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 125 
reproductive systems of these two species are quite dissimilar. The 
prostate of P. alcicornus is always differentiated and its spermatheca 
lacks the muscular investment of the bulb characteristic of 
P. simondsi. Pterodrilus simondsi, then, is a less advanced member 
of a lineage derived from ancestors much like P. missouriensis and 
P. cedrus (see p. 21) that has also produced P. distichus and P. alci- 
cornus. 
Hosts.—The following crayfishes were found associated with 
P. simondsi: Cambarus bartonit bartonii (Fabricius), C. latimanus 
(LeConte) and Cambarus species. This is the only species of 
Pterodrilus for which no species of Orconectes is known to serve as a 
host (but see p. 32 below). Moreover, only once was it found in the 
absence of C. 6. bartonii, the one record outside the Ocoee River, 
where it is associated with an unnamed species of Cambarus. 
Distrisution.—Pterodrilus simondsi is known only from the collec- 
tions taken by Mr. Simonds from small tributaries to the Ocoee River 
in Fannin County, Ga., and Cherokee County, N.C., and one collec- 
tion from a tributary to the Nottely River in Union County, Ga. 
In 1958-59 Mr. Simonds took 84 collections of crayfish from the 
Hiwassee River drainage to which the Ocoee and Nottely Rivers are 
tributary. Of his 19 stations in the upper Ocoee, P. simondsi was 
present at 14. The streams in which these stations were located are 
described as “small . . . with cold cascading waters, the bottoms 
of which are composed almost entirely of large flat stones often with 
several layers superimposed .... In such streams the water is 
clear even after heavy rains” (Simonds, unpubl. ms.). The thorough- 
ness of Mr. Simonds’ collecting efforts in similar streams of the 
Hiwassee River system to the north (75 collections, only one of which 
contained P. simondsi) leads to the conclusion that P. simondsi is a 
highly localized species. It should be searched for in the headwaters 
of the Savannah River to the east, the Chattahoochee River to the 
southeast, and the Coosa River to the southwest, but presumably 
P. simondsi is a relic of an early invasion of the area by primitive rela- 
tives of P. alcicornus that were adapted to cold, clear mountain 
streams. 
MATERIAL EXAMINED.—Types and 53 specimens from 15 localities. 
The major part of this material is deposited in the U.S. National 
Museum (USNM 36479-36485). 
Pterodrilus choritonamus, new species 
FIGuREs 7, 9 
TYPE-SPECIMENS.—Holotype, USNM 36471, and two paratypes, 
USNM 36472, from Cambarus tenebrosus Hay taken in a tributary to 
