SPIROSTREPTIDA. 91 
In Silvestri’s paper the American species which de Saussure and Humbert referred 
to the genus Spirostreptus are allocated to the following genera :— 
Alloporus, Porat, Ofv. Vet.-Akad. Foérh. 1872, no. 5, p. 43. Type A. dissimilis, 
Porat, from South Africa. 
Archispirostreptus, Silvestri, Ann. Mus. Genova, (2) xiv. p. 776 (Apr. 1, 1895). 
Type A. gigas, Peters, from E. Africa. 
Plusioporus, Silvestri, Boll. Mus. Torino, x. no. 203, p. 10 (Apr. 25th, 1895). Type 
P. salvadorit, Silv., from the Argentine. 
Urotropis, Silvestri, Ann. Mus. Genova, (2) xvi. p. 171 (1896). Type U. carinatus, 
Porat, from the Cameroons (W. Africa). 
Orthoporus, Silvestri, Boll. Mus. Torino, xii. no. 283, p. 7 (March 1, 1897). Type 
O. diaporoides, Silv., from Bolivia. 
Diaporus, Silvestri, Boll. Mus. ‘Torino, xii. no. 283, p. 8. Type D. americanus, 
Silv., from the Argentine. 
Epistreptus, Silvestri, Boll. Mus. Torino, xii. no, 303, p. 4 (Oct. 1897). Type 
EE. oscenus, Silv., from Ecuador. 
Of these, Alloporus, Archispirostreptus, and Urotropis, based upon tropical African 
species, may for the present be put aside. : 
Of the rest, based upon Neotropical forms, Plustoporus has date priority. It was 
separated from Alloporus on the grounds that the phallopod is very long and attenuated 
and the first tergal plate is simply sulcate and not inferiorly incurved. But Silvestri’s 
conception of Alloporus was taken at that time from a Paraguayan species he described 
as A. americanus, in which the phallopod is short and distally laminate, and the first 
tergal plate ridged and inferiorly incurved. In the type of <Alloporus, however, the 
first tergal plate is not incurved or ridged (carinate) and the copulatory apparatus has 
not been described. Realisation of this fact possibly induced Silvestri to establish the 
genus Liaporus in 1897 for the species americanus, which he had previously referred 
to Alloporus. Now Diaporus was diagnosed as distinguishable from Orthop rus by 
the presence of pores upon the fifth segment; but since this is not a generic character, 
as Brolemann has shown, and since Orthoporus has page priority over Diaporus, it 
follows that Diaporus is a synonym of Orthoporus. 
Epistreptus, apart from certain characters rather of specific than of generic value, 
was based upon the structure of the phallopod, which is distally bipartite, one branch 
being attenuated, the other laminate with a long attenuated process above the base 
externally. 
Silvestri’s genera are resolvable as follows: — 
Plusioporus with the phallopod long, attenuated, and not branched. 
Orthoporus with the phallopod shorter and distally laminate, but not otherwise 
branched. 
Epistreptus with the phallopod long and at least biramous, or two-branched. 
N2 
