PLATYRACHUS., 145 
show considerable resemblance to P. mexicanus, Lucas, as figured by Saussure ; but in 
the latter the pore is far removed from the margin. It appears to me to be almost 
certain that Attems described examples of this species as P. mexicanus. These 
specimens are in the Berlin Museum, but have no locality attached. I cannot find 
in his description of them a single reliable character by which they can be dis- 
tinguished from the specimens I have described above as P. montivagus. On the 
contrary, they differ apparently in many points from the typical and only known 
example of P. mexicanus (cf. supra, p. 140). 
9. Platyrachus propinquus. 
Platyrrhacus propinquus, Carl, Rev. Suisse Zool. x. p. 665, t. 12. figg. 80-82 (1902) *. 
This species is described as very nearly related to P. montivaqus, which it closely resembles in colour, in the 
structure of the legs, sternal plates, caudal process, and sternum of anal segment, and other points; but 
the yellow of the keels is not sharply defined from the brown of the rest of the upper surface ; the first 
tergal plate is markedly wider, with the angle more produced; it is evenly convex above and has a lightly 
concave posterior border ; the lateral borders of all the keels are much less strongly toothed, with the pores 
small and about twice their diameter from the lateral border. Finally, the phallopod is thinner, and 
when seen in profile shows a much greater space between the seminal stile and the terminal auxiliary 
branch, which is also more curved. 
Length, 2,76 millim., width 13-14. 
» 6, 65-73 ,, » 10-18. 
Hab. Costa Rica, Las Delicias, Santa Clara, 300 metres (Biolley 1). 
10. Platyrachus stenopterus. (Tab. X. figg. 8-8 c.) 
Platyrrhacus stenopterus, Brélemann, Ann. Soc. Ent. France, Ixxiv. p. 843 (1905) '. 
As in the case of P. montivagus, I find that the examples I identify as P. stenopterus differ, according to 
Brélemann’s description, from the type of that species in having some of the anterior sterna armed with 
spiniform or subspiniferm tubercles, He also says that the third segment of the leg is shorter than the 
width of the sterna in the middle of the body, which is not the case in my specimens. His description, 
however, was based upon a single female example, apparently defective in colour and of small size. 
Except, however, in the particulars mentioned, my examples agree so well with his detailed description 
of the type that I cannot but conclude they belong to the sume species. The male was not previously 
known. For these reasons, and making allowance for the possibility of my determination being erroneous, 
I have described my specimens at some length. 
Colour very nearly the same as in P. bivirgatus, but the brown band on the sides of the upper surface 
broader, each about as broad as the median pale area, or only a little narrower, and at least twice the 
width of the pale area on the external half of the keels; a yellow patch on the crown of the head ; no 
vertical yellow stripe on the labrum; caudal process yellow ; legs, antenne, and sternal areas yellow or 
yellowish-brown. Body nearly as stout at the posterior end as in the middle; the posterior end more 
truncated than is usually the case. Dorsal surface strongly convex ; keels small, their upper surface sloping, 
arising about the middle of the side; their anterior edge from the 11th backwards lightly convex, 
strongly convex only on the 17th or 18th segment. Posterior border lightly concave on the 4th and 
becoming more and more strongly concave to about the 17th,.owing to the increase in the length of the 
posterior angle. Their border finely serrulate from about the 5th segment. Anterior angle of keels 
rectangular but rounded ; posterior angle a little acute on the 5th, and becoming more and more spini- 
form back to the 17th, but the spiniform process only surpassing the level of the posterior border of the 
terga from about the 10th segment ; lateral border armed with from about three to five small tuberculiform 
BIOL, CENTR.-AMER., Diplop., October 19U9. U 
