124 Mrmoirs of the littimn .ytuxnim. | \'ui.. \'II. 



Till* I'a.K.snli(l fuuiia of the MuluccaN \h cloHcly alli«>«i tn tliut <if New Uuiiirn, uiul rtoverul 

 i*j»iHi»v« liiivo Ikhmj reconliHl um coninntn to both. In th»* geiius (ioniitas, howcviT, it is 

 nt»tt>wortliy that of the two «jMMio.H with iiio>t primitive inentiiiii the one witli roiiiplcte 

 <lt>iitition i.s only known from Now (iuinni ; whih* of the tliree <onunon hpccic« with more 

 highly ?«|H'i-iah7.e(l mentum the one witli the most primitive dentition seems to l>e i-onfincd 

 t«» New (iiiinea and the other two to the MohHcas. Siniihirly. in the genus /xi/m*;i'M, 

 speeies with normal elytia appear to l>e «'oniined to New (itiinea ami thos«» with fusetl elvtra 

 to the Molureas. The allietl /Vt»/uHi(X7>f/(i«, in which the mandihies are m<Mlifie<l instead 

 of the elytra, behings however to New Ciuinea, ami, althoiifrh it is undoubtedly more 

 widely tlistributed than any of its allies, the single record of its «M-curronce in the Moluccas 

 .shoulil be conlirme<l before if i< tiiially acceptod. f's> nil, iiisiihrnus uml Turi/niiiins i\rr ,ti\]y 

 known from New (iuinci 



The information al pidnt available rcLMr'nni; the (ii>>tributuiii nt AinerKaii aixl 

 Kthiopian Passalidae is nuuh less sjitisfactorv than that regarding the Indo-Australian 

 .subfamilies. The probable distinctness «(f the .\inerican and Kthiopian I'assalid faunas, in 

 spite of .several records to the contrary, has already been tlealt with (above, pp. lo-i i ). It 

 is perhaps worthy of note here that no Kthiopian l'as.salidae are kmnvn to have the elytra 

 united, and that in America, althoui;!) species with fused elytra attain the largest size, the 

 commonest and most widely distributed .sjjecies have .separate elytra. Among the 

 P.seudacanthinae Popilius coruutns is the largest and most highly spe<'ialized of the .species 

 with .separate elytra and is the commonest and most witlely distributed species in the 

 subfamily. Among the PnKidinae no species appears to lie e.xceptionally abundant. Anuuig 

 the Passjilinae I'tuillus Irnr/iii. I'nssaltis interstilialifi and Passahix iiiierniplus are particularly 

 abundant and widely distributed. The la.st named is probably the most abundant and 

 wi«lely distributed of all. and is also extremely variable. The group «tf species to which it 

 belongs appears to me to be the culminating point of the general trend of evolution through- 

 out its genus, a genus who.se wealth of do.sely interrelated species suggests that it bears the 

 same kind of relation to the rest of the American I'assalid fauna as Ijeptaulax does to the rest 

 of the Indo-Au.stralian. 



SIMMAKV. 



I . External Mor/>hohnjif. 



The clypeus is exposed and .separated by a suture from the frons only in the subfamily 

 P.seudacanthinae. In a few «ither genera, mostly American, it is exp<ised but unite<l 

 t«i the frons. In the majority of Passalids the whole of the upper surface of the anterior 

 jmrt of the head, between the .supra-orbital ridges and in front of the frontal ridge-s, is frons, 

 the whole of the cljiieiis being doubled beneath this out of sight (pp. 1-3. fig. i. 1-4). 



It is uncertain whether the inner and outer marginal tubercles of the I<eptaulacinac 

 ore homologous with the inner and <»uter tubenle.s re.s-peetively of other Passjilidac 



<VV V4). 



The dentition is reduced only in .somewhat highly specializwl forms. In Aujerican 

 bubfamilie.s it seem.H to be aHMM-iated with the loss of the habit of flight, and to come about 



