ORTHOPORUS. 93 
genera are African; and the type of Alloporus was only dismembered by Porat 
from the African species he referred to Spirostreptus, a species to which Silvestri 
subsequently. gave the name -Archispirostreptus, because it possesses pores on the 
fifth segment. If this reasoning prove to be correct, the following synonymy will be 
established: Alloporus = Archispirostreptus = Plusioporus = Gymnostreptus. And if, 
following Brédlemann’s example, we refer all the Neotropical species to one genus 
with or without subgenera, that genus may have to take the name Alloporus. For 
the present at all events, however, since the subdivisions proposed by Brolemann 
appear to be definable forms, at least so far as the males are concerned, they may be 
accorded generic rank, All the Central-American species that he has recorded and 
that I have seen fall into his subgenus Scaphiostreptus, a section for which the 
oldest name appears to be Orthoporus. 
ORTHOPORUS. 
Orthoporus, Silvestri, Boll. Mus. Torino, xii. no. 283, p. 7 (1897). 
Diaporus, id. ibid. p. 8. 
Scaphiostreptus, Brélemann, Revista Mus. Paulista, v. p. 150 (1902). 
Characters as above. 
Distribution. Central and South America. 
The Central-American species of this genus, hitherto recorded, resemble one 
another tolerably closely in external features, the principal superficial distinctions being 
differences of size, number of segments, and density of sculpturing. But within 
the limits of a single species considerable variation in these three particulars is met 
with. Even the leading character made use of in the analytical key, namely, the 
presence or absence of pores upon the fifth segment of the body, is difficult of 
detection in all cases, especially in those species where the pores are small and 
inconspicuous on all the segments. As is frequently the case in Diplopods, the best 
distinguishing features appear to be supplied by the copulatory apparatus of the males ; 
but in cases where the structure of this organ is unrecorded it is impossible to determine 
with certainty and accurately to locate, according to their affinities, the Central- 
American species described by de Saussure and Humbert and Karsch. When the types 
of these are re-examined, it may be found that the species described as new by Brdle- 
mann and myself are in some cases the same as those established by our predecessors. 
The seven species of this genus, of which I have seen examples, may be distinguished 
as follows :— 
a. Pores present upon the fifth segment of the body. 
6. Inferior portion of the first tergal plate somewhat abruptly inflected, the 
inflected area defined above by a distinct cariniform ridge, which ends behind 
in a smooth subtuberculiform prominence ; the succeeding tergal plates also 
strongly ridged ; anal sternal plate with posterior border scarcely angled. 
