

190 liULLKTIN HI, L'MTKI) STATES NATIONAL Ml'SlOUM. 



i)i<:sM(XJNATinj)Ji;. 



Copt', Joiiiii. Ac. Nat. Sim. IMiihi., ISCUi, 107. 



Ptor.vgoids wantiiij;-. Oibitospliciioid sc'i)iiiiite<l by inemluane Croiii 

 I-iootic!. Vestibiik', iiitt'inal wall o.sscumis. Jh'iitij-i'roii.s plates on tlio 

 paraspbt'iioid. Ceratoliyal articulatiiij;- with (niailratc. ('ar])iis and 

 iar.siis cartilaginous. Vortebiin opistliocd'loii.s. Jlyoid apparatus an 

 ill the IMethodoiitida". 



The peculiarity of the vertebne distiiij>uishes this laiiiily eliielly from 

 the last. Ill the only genus wliicli represents it, there are iiiiiiientus 

 peculiarities, which are not found elsewhere. Should other j,'eiiera b(^ 

 found which do not possess tliciii, the above diaj-nosis would probably 

 be the proi)er test of their family allinities. 



The distribution is continod to the eastern district of the nearctic 

 realm so far as yet known. 



The Thoriida' only dill'er lioiii the DesnioKiiathida' in the o.sseons 

 carpus and tarsus. The single genus Thorius Cope is included by 

 iJoulenger in the Desmognathida'. Thorius has a boletoid tongue like 

 Spelerpes, and the parietal region mostly membranoiis. Toes, 1-5. One 

 species, T.pcitnatulus Cope, of small size, from E. Mexico. 



DES:\IO(JNATnUS Baird. 



.JoiiMi. Ac. .Nut. Sci., I. •JSj.-J-jr. : Gray, Cut. I?rit. Mas., isr.ii, iii ; (.'ope, 

 I'loccfd. Ac. Pliila., l-^Oll ll'i : Straiicli, Salam., j). 72 : 15(iiilcnj,'cr. 

 Cat.Hatr. Sal. IJiit. Miis. -(Lii, \^S>, p. 77. 



Premaxillaries united, embracing a fontanelle ; parii'tal bones o.ssi- 

 lied. rretVontsil bones wanting. ()ccii»ital condyles on cylindric i>ed- 

 estals. Temporal muscle arising only from the atlas, with ii tendinous 

 external margin and insertion, i)assing freely over the parietal and 

 I)rootic bones. Tonguti attached, except by its lateral and posterior 

 margins. V^oinerine and sphenoidal teeth present. J)igits distinct, l-"*. 



The absence of o. prefrontale does not ai)iiear to be the result of its 

 confluence at any late [)eriod with thenasale; its ordinary position is 

 traversed by the frontal suture. Tiie frontal bone is decurVed, and 

 closes the preorbital aspect of the super[)alatal vacuity, usually opsii. 



This marked genus, so aliundantly represented by individuals in the 

 eaMtern district of Xorth America, is not admitted by either Diimeiil 

 (u- Ilallowell, probably becaii.se it dojs not dill'er in external characters 

 from riethodon. It is anexcellent illustration of the error of adhering to 

 external characters only, iii tlieexitlanatioii of the relations and allinities 

 of organized beings, except for a liiniteil range. Tlie examination of 

 the .skeleton of six'cies of this genus utterly changes tho imi)ressions 

 produced by a consideration of tlie extcrnil cliara(!ters. It may bo 

 stated aschar.icteristic of the Ijatr.uihia in general that their iiflinities 

 can not be determined without study of the skeleton. 



