INTRODUCTION. 



TlFK class of Hinls (.Ivrs), as rojirosoiitod in tlio jnxwiit n,ne of tho wdil,!, 

 is composed of very many siH'cies, closely rclalcd i\num<^ themselves ami 

 (listin,t,'iiislu;(l by numerous cliaraclers common to all. For the puriioscs df 

 the present work it is hardly necessary to attempt the iletinitioii of wiiat 

 constitutes a liird, the veriest tym l)ein<^- ahle to decide as to the fact in 

 regard to any \(n'th American animal. Xevertjielcss, for the .-^aice of ljiv;'' -r 

 completeness, we may say that, comjiared with other classes,' I'.ji'ds m 

 iihranchiate vertelirates, with a hrain lillin.u' the cranial c'vity, tiie cerehral 

 portion ol' which is moderately well developt'd, the corpora striata connected 

 liy a small anterior commisNure (no corpus callosum develoiiedi, proseii- 

 cephalic hemispheres lurye, tiie optic hii.es lateral, the eerel)elluiu trans- 

 versely multitissured; the lun-s and heart not separated i.y a diaphraum 

 from the ahdominal viscera; aortic arch sini-le (the ri.^lit only liein-' d.^vel- 

 oped); Idooil, with imcleated red corjaiscles, uiider-'oin-- a complete Ciivnla- 

 tion, beiny received and transmitted by the ri-ht half ,p|' the (luadrilocular 

 heart to the lun-s for aeration (and thus warmed), and afterwards returned 

 by Ihe other half throu.-h tla; system (there being no communication be- 

 tween the arterial and venous portion.s) ; skull with a sin-le me.lian convex 

 condyle, chielly on the basi-occipital (with the sutiu'es for the most jiart early 

 oiiliterated) ; the lower jaw with its rami ossifyin-' from several points, coin 

 nected with the skull by the intervention of a (piadrate bone (homolo-cais 

 with tlu; malleus) ; i.elvis with ilia i.rolon-ed in front of the acetabulum, isehi^, 

 and pulses nearly parallel with each otlu'r, and the ischia usuallv .separat.'d: 

 anterior and ]..,sterior memb.'is much dillerentiated : the former modilied for 

 Ih-ht, with the humerus nearly paiallel with the axis of the bodv and c.m- 

 eeah'd m the muscles, the ra.liusand ulna distinct, with two persistent carpal 

 bones, and two to four dioits ; the h-s with the bones peculiarlv combined 

 (\) the proxmial tarsal bones cah's.'iuM' with the a.ljoinin- ti'bia, an.l ^'l) 

 the distal tarsal coalescing with three (sec.aid, thii'd, and f.airt'h) n.eta- 

 linsals (the first metatarsal beiii^' free), and forudn- Ihe s,,-ealled tarso- 

 iiietatarsus ; dermal appenda-es .levelope.l as feath.irs ; oviparcais, the e--s 

 bemn- iertili/ed within the bo.Iy, excluded with an oval, calcareous shell, i'md 



MV.. ,uv iiM.l.tnl t„ lV„l,.,ss„i' Tli.MHl,,,-,. N. (iill lor tl„. p.vs,.„| ar,.,«u,l .,r tl„. ,l,Mn.,l,iiMi,'s 

 "I till' cl;iss ol limls ;ls .l|slill;riii.sllC(l flolll otlllM' ViTtclllalcs, ]l,ijfcs XI -XV. 



