The Milliped Family Hirudisomatidae 
in the New World (Polyzoniida) 
Rowland M. Shelley 
North Carolina State Museum of Natural Sciences, 
P. O. Box 29555, 
Raleigh, North Carolina 27626-0555 
Abstract — In the New World, the milliped family Hirudisomatidae 
is represented by Octoglena Wood, with five species, and the monotypic 
new genus, Mexiconium. Octoglena bivirgata Wood, O. anura (Cook), 
n. comb., and O. prolata, n. sp., are contiguous along the Pacific 
Coast from British Columbia to Santa Cruz County, California; O. 
sierra, n. sp., is a localized, allopatric species in the Sierra Ne- 
vada foothills; and O. gracilipes (Loomis), n. comb., occurs in the 
eastern United States from South Carolina to Tennessee and Ala- 
bama. Mexiconium absidatum, n. sp., the first record of the fam- 
ily from Mexico, occurs at a high elevation in the Sierra Madre 
Oriental, Vera Cruz. Octoglena bivirgata displays three dark dor- 
sal stripes, and M. absidatum exhibits a dark, middorsal stripe; the 
other species are pale yellowish to white. The following new syn- 
onymies are proposed: Hypozonium Cook and Euzonium Chamberlin 
under Octoglena, and H. arnaudi and E. crucis, both by Chamberlin, 
under O. bivirgata. The Hirudisomatidae represents an Ancient Holarctic 
faunal assemblage that spread across North America from east to 
west, and southward into Mexico, and has experienced consider- 
able extinction. Octoglena is one of five Nearctic genera exhibit- 
ing east/west disjunctions, and a secondary center of evolution exists 
along the Pacific Coast. Relationships within Octoglena are gracilipes 
+ ( sierra + (anura + (prolata + bivirgata))). 
In the Western Hemisphere, the milliped order Polyzoniida is 
represented by the pantropical family Siphonotidae, with two genera 
in South America and the common synanthrope, Rhinotus purpureus 
(Pocock), in the West Indies, Florida, Louisiana, and Central America 
(Hoffman 1977, 1980), and the Holarctic families Polyzoniidae and 
Hirudisomatidae, in the eastern and western United States. The latter 
spreads northward into coastal British Columbia, and an allopatric 
species occurs in the Sierra Madre Oriental, Vera Cruz, Mexico (Fig. 
1). The east-Nearctic polyzonioid fauna comprises six species of Poly- 
zonium Brandt (Polyzoniidae) (Loomis 1971; Shelley 1976, 1988) and 
one hirudisomatid that was erroneously placed in this genus and family. 
The western fauna of this order has never been examined and presently 
consists of seven genera and ten nominal species (Chamberlin 1954, 
Brimleyana 23:103-143, December 1995 103 
