E! 



;ii 



1 1 



r 



2.0O 15ULli:ti.n :!i, united «tati:s national musiujm. 



In .strict ivlLMviice to the extension of the webs the following parallels 

 may be drawn : 



AltCIIKItl. 



liana. 

 ll(>[iloliah!icliiiH. 



I'.vxi<!<'i>lialuH. 

 Lo|)li)|i(>lis. 

 llyperoliMN. 

 Hrtt'ri);;lo8.sa. 



CasHina. 

 Ilciiiiiiiantis. 



Psciidis. 



MjM>l>ll.V('M. 



Ci'iatoiilir.vN. 

 Il.vla. 

 Ilyli^lla. 

 A<!ri«. 



C.VHti!;naflms. 

 I'aliiilii'ola. 



IvANIH.i;. 



External motatarsal free: 



A(|iiati('. 



."^iilitossoiial. 

 Extdiiial iiii'talarsal attuclicil : 

 I'Vct \vt'l>lit'(l — 



niiirowiiifj. 



Arliorral (voin. tfctli). 



Arl»)it'al (ill) voiii. Ii'ctli) 



Ai|iiatif. 

 I'''"('f not \v('ltl)('(l — 



'I'ciTi'.stri.'il. 



TciTL'Htiial, spmrcd. 



It i.s, however, remarkable that the ranirorni treefio^s nearly always 

 have the external metatarsal bone free; the ai'ciferoiis always bound. 

 The terminal i)halanfies ot the latter are eonslrn<'ted on a ball and daw 

 type. In the former they are X shaped or biliii(!ate, except in (he single 

 West AlViean {{enns Leptopelis. where the Sonth Ameiiean tyi»e is re- 

 l»eated. 



I have also diseovered another series of parallels wliieh the {ji-nera 

 of most of the families of the Salientia present, in (he de;,'ree of ossi(i-~ 

 (nation of the sn|>eiior (iranial walls,* In the least-ossilicd crania wc 

 llnd the snperior pari of the ethmoid still cartilaginous, (he snperior 

 wall of the brain-ca.se meml)ranons, and the prefrontals represented by 

 narrow lateral splints of bone. In jj^encra of slijihtly advanced type 

 the roof of the eihmoid is ossified, and the prefronta's aie witter. In 

 better developed ^eneia the frontoparit-tal bones ossify and close tln^ 

 Ibutanelle. Tlu> lii;;lier ossilication shows itself in an exostosis of the 

 snperior cranial walls, which, in further sfajics, involves the sUin, so 

 that it is no lonf;er free fiom the craninm. The next stafje roofs over 

 the temporal mn.scht with bone, and the hi<;hest stajje, known only in 

 a ^icnusof Unfonida' (Otaspis ('<»pe), inclo.ses the membrannm (ympani 

 l)eliind. TIh^ following;" table expresses tln'se facts. 



These series };ive an excellent illnstiation of the developmeiM of a 

 single chara(;ter independently of othei- characters, and show how the 

 generic eharactt'rs ori;;inat»^ (piile inilependently of all others. 



'.S'eNal. Ilisf. h'fv., l-li:.; I'niiictl, Ac riiiia., l-ilW (on llio <>iiM;in of Cciiciii); 

 Orij^in of tin; I'itlest, IS-^r, p. •Jl^', I'lati^j iv ami v. 





11 



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