114 DIPLOPODA. 
The Central-American genera of this group are referred to two subfamilies, which 
may be defined as follows :— 
a. Segments smooth ; their keel-bearing portion posteriorly elevated and divided 
into definite oblong areas by short longitudinal sulci; no pectinate rim on 
the posterior border of the segments . . . . 6 « +e + + « + «© ONISCODESMINA. 
a’. Upper side of the keel-bearing portion of the segments granular or tubercular 
and often thickly hairy; a distinct rim of fine pectinations on the posterior 
border of the segments. . ee ee ee ee ee CyRrropESMINZ. 
Subfam. ONISCODESMINA. 
LIGIODESMUS, gen. nov. 
Allied to Oniscodesmus, with the second segment much the largest of the series and expanded laterally. All 
the segments, with the exception of the first and last, marked with a transverse sulcus, behind which 
the tergal plates are ornamented with longitudinal sulci dividing their posterior portions into a number 
of oblong areas; these longitudinal sulci extend on to the keels. Pores ou segments 5, 7, 9, 10, 12, 18, 
15 to 19, situated near the middle of the upper surface of the keels. Tergal plate of the twentieth 
segment transversely oblong, about twice as wide as long and wider than the keels of the nineteenth 
segment which embrace it laterally. 
Type, L. pusillus. 
To the group to which Cook (Pr. U.S. Nat. Mus. xxi. pp. 454-456, 1898) restricted 
the family name Oniscodesmide, three genera were referred by him, viz.: Oniscodesmus, 
type oniscinus, Gervais & Goudot, from Colombia ; Lignydesmus, type rubriceps, Peters, 
from Colombia; and Detodesmus, type aurantiacus, Peters, from Venezuela. ‘The last 
two Attems does not admit as generically distinct from Onzscodesmus. This new form 
differs from all of them in having the tergal plate of the twentieth segment transversely 
oblong, twice as wide as long, wider than the keels of the nineteenth, and with its 
posterior border lobulate. In the case of the other species mentioned the tergal plate 
of the twentieth is minute in Oniscodesmus ; and although larger and subspherical in 
Lignydesmus and Detodesmus, it is scarcely wider than long and barely as wide as the 
keels of the nineteenth which curve semicircularly round it. In the large size of the 
twentieth tergal plate the genus Ligiodesmus serves to connect the above-mentioned 
genera with those that Cook referred to the Cyrtodesmide, namely Cyrtodesmus, 
Oncodesmus, and Cyliocyrtus. 
1. Ligiodesmus pusillus, sp.n. (Tab. VIII. figg. 6-6 e.) 
Colour obscurely fuscous, keels paler, legs flavous. 
Head punctulated. Antenne moderately long, incrassate, the segments increasing in thickness to the fifth, 
which is longer than the second and fourth, and about as long as the third. Second tergal plate greatly 
expanded laterally, apparently as in Detodesmus aurantiacus, Peters, but differing from that species in 
having its posterior border distinctly areolate, as in the two species of Oniscodesmus and in Ligny- 
desmus rubriceps. The pores not raised as in the latter, but sessile as in the two species of 
Oniscodesmus  Oopulatory organs of the same type apparently as in Detodesmus aurantiacus, divided 
distally into two branches, the inner forming a recurved hook and terminating in the slender seminal 
