LIGIODESMUS.—ONCODESMUS. 115 
stile, the outer having the form of a foliated lamina which posteriorly sends upwards a long and slender 
process, 
Length 6°8 millim., width 2-5. 
Hab. Mexico, Teapa in Tabasco (H. H. Smith). 
Subfam. CYRTODESMINZ. 
The two recorded Central-American genera of this group may be distinguished as 
follows :— 
a. Pores present; tergal plate of twentieth segment quadrate, broader than 
long and not in any way concealed by the keels of the nineteenth ; keels 
with a deep notch in the posterior border near the base. . . . . . OncopEsmus. 
a‘. Pores apparently absent in the type species; tergal plate of twentieth 
segment narrow, pointed, covered to a great extent by the enlarged 
and backwardly extended keels of the nineteenth segment ; no notch at 
base of posterior border of keels. . 2. . 2. 2. we ee) ee) he) )06UCRYPrURODESMUs. 
ONCODESMUS*. 
Oncodesmus, Cook, Brandtia, 1896, p. 28; Pr. U.S. Nat. Mus. xxi. p. 458 (1898). 
Allied to Cyrtodesmus, Gervais (Ins. Apt. iv. p. 92, 1847), but differing in having the dorsal surface of the 
segments distinctly tubercular and hairless instead of thickly hairy and closely granular; also in having 
the lateral portion of the second segment much more widely expanded and the pores sessile instead of 
being raised on definite papille. 
Mr. O. F. Cook established this genus and differentiated it from Cyrtodesmus after 
a somewhat hurried examination of the types of C. velutznus and C. granosus in the 
British Museum. He appears to have overlooked the fact that the segments in the 
type of C. velutinus, to which he restricted the name Cyrtodesmus, are densely granular 
as well as hispid or hairy, for he merely describes them as being “ densely velvety 
pilose,” and distinguishes Oncodesmus, based upon C. granosus, from Cyrtodesmus 
partly because “ the surface of the segments, instead of being densely and uniformly 
hispid, is merely beset with coarse granules.” As a matter of fact, C. velutinus is 
granular and C. granosus tubercular. A difference, however, which he does not appear 
to have noticed is that the pores in C. granosus are sessile and not papillate. The 
type of C. asper, Peters, a species which Cook made the type of his genus Cyliocyrtus, 
also has the pores papillate and the segments hispid as in C. velutinus; but the 
segments are tubercular and the lateral portions of the second widely expanded as in 
C. granosus. It thus stands midway in its charactars between the other two. In all 
of them the general form of the body is like that of Ligiodesmus and Oniscodesmus, but 
they differ totally in the sculpturing of the segments and in having a deep notch in | the 
posterior border of the keels. 
* Incorrectly given as Omodesmus in Zool. Record, 1898, Myr. p. 11. 
