18 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 125 
This material, for the most part, is deposited in the U.S. National 
Museum (USNM 36138-36159). 
Remarks.—The holotype of P. mezicanus Ellis (1919) from 
Mirador, Veracruz, Mexico, is poorly preserved, making a study of the 
internal structures impossible; it was separated from other bran- 
chiobdellids by Ellis (1919, p. 254) on the sole basis of the ‘‘simple 
four-horned appendage like that on the same segment of P. distichus.”’ 
I have collected branchiobdellids in Mexico and unsuccessfully have 
tried to locate Mirador. Among the 64 collections from Mexico that 
I have studied, there are no specimens that can be assigned to the 
genus Pterodrilus. I have, therefore, with considerable hesitation, 
referred my material from the Ozarks to P. mexicanus. The possibility 
remains that a future discovery of P.mezicanus at or near the type- 
locality will necessitate the renaming of the Ozarkian animals. 
Pterodrilus hobbsi, new species 
Fiaurss 4, 9 
TypE-sPECIMENS.—Holotype, USNM 36486, and five paratypes, 
USNM_ 36487, from Cambarus rusticiformis Rhoades, Orconectes 
quvenilis (Hagen), and O. placidus (Hagen) taken from Spring Creek, 
1.4 miles north of the Putnam County line on State Highway 43, 
Overton County, Tenn., by Perry C. and Virgie F. Holt, July 26, 
1961. 
Draenosis.—Dorsal ridge present on segment VIII, bearing fanlike 
projection with five prongs, other segments without dorsal ridges 
and projections; bursa small, ovoid, length less than half body diam- 
eter; ejaculatory duct of normal length; spermiducal gland relatively 
large; prostate about %4 diameter of and subequal in length to sper- 
miducal gland; spermatheca clavate, bending dorsally over gut. 
Erymo.tocy.—I take great pleasure in naming this species in honor 
of Dr. Horton H. Hobbs, Jr., as a token of my gratitude for the many 
years of friendly help he has given me in my study of the branchi- 
obdellids. 
Description.—In shape and size, P. hobbst is much like other 
members of the genus, differing from all except P. choritonamus and 
P. mezxicanus in the absence of ridges on the prosomites of all segments 
except the eighth. The dorsal projection of this segment is fanlike and 
bears five tapering prongs of which the median is the longest. The 
length ranges from about 1.3 to 1.7 mm. 
The spermiducal gland is not markedly different from that of 
P. mexicanus; the prostate, however, is distinctly vacuolated; that 
is, it is histologically differentiated, but there is no distinct prostatic 
bulb. The two organs are broadly joined and often the spermiducal 
