DIGESTIVE SVSTEAT 145 
All the Ratit# agree in having the second loop right-handed, 
and the third left-handed ; this is a feature which occurs again only 
in the Crypturt, Gallinw, Opisthocomus, and in the Cuculide. More- 
over, as with the exception of the duodenum none of the loops are 
closed and well defined, the Ratitz represent in this respect the 
lowest avine type. ; 
The Galline form a well-defined group; lowest among them 
stand the Neotropical Cracidx, through which they lead towards 
the Crypturi. The Gallinw have also an unmistakable resem- 
blance to Opisthocomus and thence to the Cuculide. 
The Turnices, to which belongs undoubtedly Pedionomus, are 
traceable to a Ralline or low Gralline stock, with assumed 
plagioccelous characters of the second loop. 
The periccelous assemblage is large. It is typically represented 
by the Waders, of which the Limicole and the fallidx form the 
principal groups. 
The Rallidz with Otis and Gus are connected with the Turnices, 
more distantly with the Crypturi, and still more so with Apteryz. 
Dicholophus is in all points a Gruine form, like Psophia, and cannot 
be separated from them. hinochetus contains Ralline, Limicoline, 
and Ibis-like features ; the only bird which it resembles somewhat 
closely in its very peculiar intestinal convolutions is Podica. 
The Limicolz agree with the Laridx, and also with the Columbx 
in all essential points. Each of these three groups contains a number 
of forms which lead in an unbroken series from the typically peri- 
ccelous birds with four alternating loops to the typically mesogyrous 
birds. Most Columbx and Laridz are mesogyrous, but Sterna and 
its allies represent periccelous or lower forms. Neither granivorous, 
nor insectivorous, nor piscivorous habits have exerted any appreciable 
influence upon their intestinal convolutions, although of course the 
stomach and the ceca are affected. The presence of the crop of the 
Columbz# is repeated in the granivorous Limicoline genera Attagis 
and Thinocorys. 
Numenius approaches in various ways the Ibises, whence a con- 
tinuous line can be traced into Platalea and Phenicopterus on the one 
hand and into the Pelargi proper on the other. 
Rather different from the Limicole are the Pteroclidx. They 
have four loops, which are all closed, left-handed, 7.¢. isoccelous, and 
straight ; the second and fourth loops have their apices turned back, 
and especially the terminal end of the second resembles somewhat a 
plagioceelous formation. The Pteroclide have consequently various 
points in common with the Rallidx, Limicolxe, and Columbe. 
The Alcidz are pericelous and strictly orthoccelous ; they agree 
with the Laro-Limicolx in the configuration of their first three loops, 
but they differ from them in the number of loops, which is at least 
six, the last three of which are left-handed. They approach in this 
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