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tUE ISATRACniA OF NORTH AMKRICA. 207 



I. Caviiiu tympaiii and tympaiiiiin waiitinj;. Xiiiliistciiiiiiii with an ossiiiiMl inoxi- 



nial Nlylc. Ciincilonii Ixino and .slu-atli well (Icvi'luiii'd. I'upil iri'cl. Toes 



\Vld)luMl. 



Derm involvt'd in cranial ossilication. Temporal fossa with a stn.ii}? roof. 

 V(nn(!rinc teuth : no parotoid glands Cnllriiw^. 



Derm involved in cranial ossilication. No roof over the temporal fossa, or par- 

 otoid glands. Vomcrint' Iccth I'vhthnlvH, 



Derm distinct from cranium, which is nndcvclopcd ahovc, two lateral iVonto- 

 paiietal l)ars inclosing a median fontanelle. Vomerine^ teeth. No jiaro- 



loids I)i<li)ciis. 



Cnneilbrm hono and sheath well developed. Toes more or less wehlied. 



II. Cavui!' tympani and tymiiannni present. Xipliisternum entirely cartiln^inoiis. 



IMipil ellii>tic erect. 

 Derm involved in the cephaMc ossilication, which is coinplelc. I'.irotoid j;lands 



and vomerine teeth s'tdf/u'oyiH.v. 



Derm distinct from cranium, which is usually only ossilied superiorly in two 



sujierciliary bars. I'jirotoid glands and vomerine teeth Siwu. 



Tlio oxtroiuo of diverj^ciice of the sorie.s of tlii.s family is, tluMi, that 

 represent i II j;' its type in a pre einiiient dejiree. This is seen in the j^cmi.s 

 C(»ltrii>es wliere liie ossilieation of tlie siii>erior eranial walls is esjje- 

 eially lhi<;kene(l, obliterates the sagittal suture, anil is e.vtentled in an 

 arch over the tempoial fossa. The anterior ossifieation of theeo(!c.yx is 

 applie<l by its axial portion beneath the axis or eentrnin of .the sacral 

 vertebra, and beeoines consolidated with it sh(utly after its eoininence- 

 Mient, fnrnishing a structure not rare among bnrrowing Aniira. Tliis 

 character is maiiitiiined in the descendiii!, scale by Peh)bates, Diihxnis, 

 S<;aphiopus, and Si)ea, Ihotigh "none of these have the temporal fos.sai 

 overarched. Cnltripes, with Pelobates and Didocns, exhibit an ossified 

 basal xiphisternal piece, while in all below it is cartilaginous, as in most 

 Ar.;ifera; the extreme position of the former is also maintained by the 

 obliteration of many portions of the auditory apparatus. The siuiceed- 

 ing form.s — Scaphiopns and Si)ea — resend)lethe first group in the toad- 

 like form and in the strong cuneiform shovel and webbed feet. 



The distiibution of the .species of the family is as follows: 



("Mltri|>(>,s .. 

 I'l'lolialtis . 



Oiilorii.s 



.Scajiliiopiis 

 Sp<'a 



The inferior dermal attachments of seven species of this family arc as 

 I0II0W.S : 



liiiloviiH calcdrulii'i, Uelly more than tialf attached. 



I'cIoIhiIch/uhchh. P'roni half to two-thirdsattached ; same in larva, with long tail ; fe- 

 mur one line lielow. 



Srniihiopiis holhroohii. Free only opjiosite sternum: thi;;h attachi'd only uelow on 

 Itasal half. 



>Sc((j»/iio^)i(.s roiirhii. Triangular free area to middle ahdomen. 



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