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246 miLLKTiN :ri, united states national museim. 



bonos may be tracod to a similar causo, t'spccially the stixvssupoii tlioni 

 at tlie moiiuMit of starting a leap and alij;iitiiiy from it. The .survival 

 of tlie elonf^ate eoracoid bone may be trat'ed to use b,\ pressure alonj; 

 its lonftitudiual axis in the a<'t of seizinj;' tlie female, and possibly by 

 stress in tlie opposite direction wlien en{ia{;ed in pusliin,v: objj'cts out- 

 wards with the fore-feet, iirodncinfi' the etVeet of elon<iati(»n. It is not 

 easy to assij^u a cause for the loss of the ])ra'sternuni and of vai ions 

 cranial bones. It has been, i)eihaps, in these comparatively uniistd 

 parts that one etfect of the jicnoral leduction in size and vioor which 

 has occurred during; -geological time since the Carboniferous and Trias- 

 sic periods, is to be seen. The loss of auditory organs is probably du(^ 

 to disuse, the i<'sult <»f subterranean life.* 



The larval life of tlie Salientia has probably undergone iniportanf 

 modifications during the couise of geologic lime. The characters as- 

 sum«'(l by tad|)oles at dilfereiit stages of their growth are not parallels 

 with known or piobably to be discovered lower forms of life, luit indi 

 <'ate that tlu' larva, likt^ that (»f the Insecta, and like the mammalian 

 fo'tus, has had a developmental history of its own. In support of this 

 view I cite the anterior jtrodu tioii of the quadrate cartilage, which 

 carries with it the eeratohyal arcth from its piimitive attachment, and 

 the idfimate shortening of the same, and the return of (he cerat(»Iiyal 

 to nearly its piimitive connection with the skull. I-'uiiher, ilie grad 

 md iiurlosure ol the (ore leg in the external branchial ehainber is to be 

 cited, the original position of the limb having been external. To these 

 maybe added the development of the epidermal stickers, of the labi;d 

 dermal comb, ami of ])eculiar dermal glands in some tadpoh's. None 

 of these peculiarities of larval life are found in the Trodelii, and (hey 

 have been gradually assumed by the lirva- of the Salientia in the comse 

 of their existence, as though (lie\ were adult animals, and ]>i(»i>ably 

 in obedience to the same kinil of laws. These aie (he interaction of 

 the animal and its environment. 



CLASSII'IGATION. 

 The natural divisions of the ISalieiitia are the following: 



I. N(i toii^iK' : ont' |)liar,\ ii;;<';il opi'iihi;; ol' tin' lliisl.'ii'liiaii tulic 



|>ti.| VMoiii lioiit's inc'io.sjriv; IjinIiicIiIiiIi t iiIm's Itdciw ; rmaiuiils and iii'Dcdracoids 

 (livcifiriif, ('"iilirclrd liy a ( ai I ila;;c wlii<li does md ovi'ilap I lial uC llii' t>|i- 



piLsili' side \iihinxii. 



IF. 'I'diijjiic |i?f.sciil ; (WMdstia ]di,ir\ iiL:i'a. 



('Ia\ i(df and t'liraciiid <>!' cacli ^idi' ruiiiirrlrd l>y a loii^il iidlii.il anlicd carti- 

 lage, wliicli (iMTlaps lliat oC tlic i>p|ii>-itf sidf : sciimla (Vic iVom llit^ ^l^llll. 

 //■(■(/( /((. 



(Ilaviidi'S and coracoids id' ln>tli sidi's ciiiniiTtril I'V a .sin;;li' nairow rnidiaii lai- 

 1 ilagt' ; si'a|)nli) artinilatrd with a siicci.ii londvli' id' - xnrciiiil.il ilnsirrilniiin. 



{'Ia\ iidi's and inraroids id" Iml li sidi's rimnrctid liy ;i MMLfio ini'diaii r;irlil.ii;(' ; 

 sraiml.i ilistinrt from nUwW I'iniiisi, nihi. 



•Seo Farts and OpiniidiM ndatin^ (i> tlir Ural, Uv .\!- \. (J. I!. II, (.nndiiii. I — . p. >',•. 



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