424 OKTHOPTEBA. 



tubercle, and the inferior branch has another tubercle above at the base. In this case 

 the cerci incline to the trituberculate form characteristic of I. atrispinum. The process 

 of the supra-anal plate of the male has a foveola at the base ; it is variable in length : 

 when long, it is curved down at the base; in some specimens it is straight and only 

 slopes downwards, in others it is shorter, forming a transition to that of I. atrispinum. 

 In the females the supra-anal plate resembles that of the males : it is strongly corneous, 

 rufous, deeply foveolate at the base, but shorter than in the males, and straightly 

 attenuated posteriorly, truncate, and bidentate or tridentate, sometimes quite short. 



JT. atrispinum has the cerci of the males truncate, obtuse, terminated by three 

 rounded stumps or tubercles, but sometimes the inner tubercle is prolonged and forms 

 a sort of blunt hook. In this case, compared with the abnormal form frequent in 

 /. furcatum, it is the superior branch of the fork which appears to be developed, while 

 in I. furcatum it is the inferior branch, the superior one being here atrophied. The 

 supra-anal plate of the male, in its typical form, is short and square (Tab. XX. fig. 21), 

 trispinose, and has a strong foveola at the base ; but in some specimens it becomes more 

 elongate, quite resembling the process of I. furcatum, only somewhat shorter (fig. 17), 

 making an evident transition to that species. These specimens, therefore, would appear 

 to belong to i". furcatum, but in the form of the cerci they agree with /. atrispinum. 

 In the females the supra-anal plate much resembles that of I. furcatum, it being 

 elongate, corneous, rufous and shining, sulcate, and with a foveola at the base ; but it 

 is more regularly triangular, more widened at the base, much attenuated posteriorly, 

 narrowly truncate, and rounded or very minutely bi- or trituberculate at the tip. 



I. atrispinum and /. furcatum might thus be regarded as one species (?), with the 

 supra-anal plate very variable in form in both sexes, and the cerci variable in form in 

 the male. 



Synopsis specierum. 



1. Mares. 



a. Lamina supra-analis in processum Ion gum, angustum, ad iuferum valde deflexum, apice 

 leviter dilatatum, tridentatumque, producta. 

 b. Lamina supra-analis concolor, angusta, supra punctata, longissima, basi angustata haud 

 foveolata. Cercorum apex incurvus conicus. — 1. incurvum, St. 

 bb. Lamina supra-analis nitida, minus longa, basi haud angustata, profunde foveolata. Cerci 

 apice furcati (fig. 19). — 2. furcatum, sp. n. 

 aa. Lamina supra-analis brevior, plana, haud decurva. 



b. Lamina supra-analis longiuscula vel quadrata, apice tridentata, basi foveolata. Cerci 



brevissimi, apice haud attenuati, truncati, obtuse tricipites (fig. 21). — 3. atrispinum, St. 



bb. Lamina supra-analis quadrata, retro leviter attenuata, truncata vel margine postico 



obsoletissime triangulato, vel tantum angulis acutis. Cerci teretes, apice conico 



obtuso. — 4. subquadratum, sp. n. 



