PLATYDESMUS. 49 
So far at least as pattern is concerned, this species resembles P. triangulifer, except 
in the colouring of the keels. In P. triangulifer these are pale, with those on each 
side of the body opposite the widest portion of the pale median triangular patches 
dark, exactly the converse obtaining in P. mexicanus. ‘The latter, moreover, is a much 
broader-bodied form, resembling P. perpictus in this particular. 
11. Platydesmus guatemalensis. 
Platydesmus guatemalensis, Brélemann, Mém. Soc. Zool. Fr. 1900, p. 112, t. 7. figg. 78-82". 
Colour: variegated reddish-brown and yellow ; a median dorsal band formed of alternating yellow and brown 
rectangular patches, each patch extending over two adjacent segments ; an exactly corresponding series 
of spots upon the keels, the intervening area of the segments deep brown; ventral surface pale. 
Head without eyes. Body broad, almost four times as long as wide. Segments of substantially the same 
form as in P. mexicanus, furnished with two rows of tubercles, which become gradually effaced upon the 
keels. Sterna broad in the middle of the body and separating the legs widely. Number of segments 47. 
Total length 15, width 4 millim. 
Hab. Guatemata (Rodriguez '). 
This species differs from all the Central-American forms known to me in the absence 
of eyes and also in colour. In the latter particular, as well as in proportions, it stands 
nearest to P. perpictus; but Brélemann’s statement that the segments of P. guate- 
malensis resemble those of P. mexicanus enforces the conclusion that the first tergite 
is widely excavated in front and not laminate as in P. perpictus. Reference may be 
made to Brolemann’s paper for admirable figures of generic characters of Platydesmus. 
Another genus of this family, namely Andrognathus [Cope, Proc. Amer. Phil. Soc. 
1869, p. 182; Bollman, Bull. U.S. Nat. Mus. no. 46, p. 187 (1893)], hitherto known 
from North America, will probably be found to extend at least as far south as Mexico, 
since the one species yet discovered occurs both in Virginia and Tennessee. This 
genus, unknown to me, is referred by Bollman and, following him, by Silvestri to the 
Platydesmide. It may be at once distinguished from Platydesmus by the suppression 
of the terminal process on the stipites and lingual lobes of the gnathochilarium, the 
absence of tubercles on the dorsal area, the large size of the keels of the fifth segment, 
and the pedunculated pores. 
Fam. SIPHONOPHORIDE. 
Head piriform, with a narrow pointed labrum. Mandibles obsolete; gnathochilarium with its sclerites 
indistinguishably fused, narrow and pointed distally, and forming with the labrum a pointed rostrum. 
Eyes absent. Antenne lateral. Somites with thick chitinized pleure. Sternal areas compressed ; basal 
segments of legs almost in contact in the middle line. Penes perforating coxe of second legs, 
Iistribution. Neotropical and Oriental Regions. 
Of the two genera that have been referred to this family, one only, Siphonophora, 
BIOL. CENTR.-AMER., Diplop., November 1903. H 
