142 DIPLOPODA. 
the same reason that I separate P. tristani from P. limonensis, although Carl accepted 
without question the truth of the statement regarding the presence of the coxal tooth 
on the legs of the sixth pair. My reasons for treating P. tristani as distinct from 
P. fraternus are that Carl says that the anal sternal plate in P. fraternus bears two 
small warts as in P. bivirgatus, whereas these warts are of large size in P. tristani, as 
they are in P. limonensis; that he describes the outer half of the keels only as yellow, 
instead of the entire keel; and, finally, that the statement that the lateral edges of the 
keels are furnished with from four to five “ ziemlich spitze Hackerzahne” does not in 
the least express the character of the armature of the keels in P. tristant, which, as has 
been said above, are in no sense sharp or tooth-like. 
The phallopods seem to be of practically the same structure in the three species 
enumerated above. 
4, Platyrachus limonensis. 
Platyrrhacus limonensis, Attems, Denk. Akad. Wien, Ixviii. p. 344, t. 14. fig. 819 (1900) *. 
Hab. Costa Rica, Pert Limon }. 
The typical male example of this species measures 116 millim. long and 18 millim. 
wide. The enumeration of its essential characters under the heading of P. tristani 
makes a repetition of the description given by Attems superfluous. 
5. Platyrachus fraternus. 
Platyrrhacus fraternus, Carl, Rev. Suisse Zool. x. p. 655, t. 11. fig. 71 (1902)*; Brélemann, Ann. 
Soc. Ent. France, Ixxiv. p. 342 (1905). 
Hab. Costa Rica, La Palma 1600 metres, Caché, Atlantic slope 1000-1100 metres, 
San José, Port Limon (Biolley 2), Cariblanco 600 metres (Lankester °). 
Specimens measured by Carl were from 90-100 millim. long and from 16-19 millim. 
wide. Brélemann, however, points out that his examples from Cariblanco are smaller 
than those from La Palma, while adults from Caché do not exceed 60 miliim. in length. 
For the distinctive features of this species, see above under the heading P. tristani. 
6. Piatyrachus bivirgatus. 
? Polydesmus (Odontodesmus) python, Peters, Monatsb. Akad. Berlin, 1864, p. 543°. 
Platyrrhacus bivirgatus, Carl, Rev. Suisse Zool. x. p. 652, t. 11. fig. 65 (1902) *. 
Closely allied to P. limonensis, P. fraternus, and P. tristani, but totally different in colour. The greater part 
. of the upper surface is yellow with a large brown patch on each side of the tergal area, where it passes 
into the keel; the patch forms, with the brown area of the sides of the prozonites, a continuous brown 
band extending from the Ist to the 18th tergal plates; each patch is a little narrower than the 
yellow area of the keel and about half the width of the median yellow area of the back; the caudal 
process of the anal tergal plate is yellow, and there is a yellow patch on the summit of the head; the 
ventral surface of the body is also paler than in the others. 
‘The tubercles of the anal sternal plate in the one specimen I have examined are considerably smaller than 
