191M.] F. 11. CravelV: Pnssalidrrr of the World. 9 



Mantmhilits aipitalis,^ Hlackljurii. iltllU, pp. •_'(i<i--_>ln. 



siibMiqiiiis. Tryon, 1892. 

 Pelo/is triiiiiipliator, Zang. I!t()l6. pp. 182-181. 

 Ple.stfieiiii.1 mandibiiltin'K. Heller. 1900, p. 11, pi. fig. 5. 



.. sciilelloj)inicl(iliis, Zang, 1903r/, p. 339. 



Prolomocoehis Sternberg}, Zang, 1905fl, pp. 236-238. 

 Tristorlhus ixipitaniis. Heller. 1910. p. I'), pi. fig.s. 1.j-1.>j. 

 Trislorl/iiis piniclicollis. Heller. 1910. p. 353. 



In view of tlic striking ((inelation wliieii has been shown to exi.^t, in certain Indo- 

 Australian Passahdae, between chissification and distribution (Gravely, 19146), it is natural, 

 when seeking tor sound princiijles on which to base the classification of the family as a 

 whole, to consider first whether it may not be po.ssible on purely morphological grounds to 

 regard the American and Ethiopian Pas.salidae respectively as .series independent both of 

 one another and of Indo-Australian forms. 



It will be remembered that among the Indo-Au.stralian Pas.salidae the Aulacocyclinae 

 standby themselves, widely separated from all other forms (Gravely, 1914c, pp. 191 -192). 

 They are also widely separated from American and p]thiopian forms and need not be further 

 considered in this comiection. In all other Indo-Australian Pas.salidae, except certain hiorhlv 

 a.symmetrical oues with reduced dentition, the lowest terminal tooth is directed inwards 

 and is situated beside the anterior lower tooth, which is broadly triangular as seen from 

 above and tends to be flattened above and below. In American and Ethiopian forms, on 

 the other hand, none of which are a.synuuetrica], either the terminal teeth are situated in a 

 line one above another; or the anterior lower tooth (on the right side at least) is more 

 columnar and tends to be flattened in front and behind, or may be concave behind much 

 as it the Aulacocyclinae, or both characters may be present. These characters are more 

 marked in some species than in others, but in greater or le.ss degree thev are of universal 

 application ; and they are associated with various other, often more strikino-. differences 

 of more limited application. 



The reduction of the dentition takes place mainly in highly specialized genera of the Iiuln- 

 Australian and .\merican series, genera whose relationships are, as a nile, clearlv indicated bv 

 other characters. Among the former it is confined to the more highly asymmetrical genera, 

 and among the latter it is found chiefly in genera composed wholely or in part of flit^htless 

 species. It is easy to follow the manner in which the reduction is carried out in the former ; 

 but in the latter it is often more ditticult, the reduction being more abrupt. In the Indo- 

 Australian series it is always due to the fusion of the anterior lower tooth with the lowest 

 terminal tooth (see Gravely, 1914c, text-fig. 7, p. 314). In the American and Ethiopian 

 series, with the possible exception of the genus Procuhts, it seems always to be duo to 

 the fusion of the two lowest terminal teeth, though this is apt to be accompanied bv a 

 dorsoventral flattening of the anterior lower tooth, which thus loses its distinctive shape. 



The reduction of the dentition in the American and Ethiopian series mav most 

 conveniently be illustrated by reference to the genera of the /Voo»/c/i)/(/<'s group of Pa.s.silinae 



' Maslochilus capilnli". Wackbxirn = Episphenoidcf ipiaef!io>'>'. Kiiwcrt. 5?oo Znng. 19l.k">c. p. 22?. 



