104 
Rowland M. Shelley 
Fig. 1. Distribution of the Hirudisomatidae in the New World, showing the 
areas occupied by Octoglena in the eastern and western United States and 
British Columbia, and the single site of Mexiconium, denoted by the dot 
and arrow, in Mexico. The dot in California represents the two localities 
of O. sierra. 
Chamberlin and Hoffman 1958). Hoffman (1980) and Shelley (1988) 
referred Octoglena and O. bivirgata , both authored by Wood, to the 
western fauna and the Hirudisomatidae, because its striped color pattern 
(Wood 1864, 1865) is displayed by two California hirudisomatids, 
Euzonium crucis and Hypozonium arnaudi, both authored by Chamberlin, 
whereas no eastern polyzonioid is so marked. Studies are progressing 
on the west-Nearctic Polyzoniidae, so this contribution addresses the 
Hirudisomatidae and transfers the east-Nearctic representative into Octo- 
glena; I also erect a new genus, Mexiconium , to accommodate the 
Mexican species. Octoglena is therefore a continental taxon and similar 
to Brachycybe Wood (Platydesmida: Andrognathidae), Orinisobates 
Lohmander (Julida: Nemasomatidae), Scytonotus Koch (Polydesmida: 
Polydesmidae), and Ergodesmus Chamberlin (Polydesmida: Nearctodes- 
midae) in exhibiting east/west disjunctions (Fig. 1) (Gardner 1975, 
Enghoff 1985, Shelley, 1993, 1994a). I do not address here the larger 
