ANATOMY OF THE SHOE -BILL 66 x 



The duodenum is a definite loop, tending to be rather wide 

 and further sub-divided in the Falooniformes, to be excessively 

 long, twisted and rolled up with the first loop of Meckel's tract 

 in the Ciconiiformes, to be very long, narrow and with a minor 

 loop on its proximal limb in the Ardeiformes. In Balceniceps, it 

 is not highly specialized, but the differentiation it displays is 

 more like that in Herons than in Storks, especially in the forma- 

 tion of the secondary expansions at the base of its distal limb. 



In the same assemblage Meckel's tract is long, and is suspended 

 i-ound the circumference of an almost circular expanse of mesen- 

 tery which grows oat from a very short portion of the primitive 

 dorsal mesentery It is roughly symmetrical about the main axis 

 which runs out to the remnant of Meckel's diverticulum, the 

 latter being invariably present. On the proximal half of the 

 tract there is a tendency to the formation of three minor loops 

 between the duodenum and Meckel's diverticulum. These tend 

 to remain comparatively simple and similar in the Steganopods 

 and in the Falconiformes. In the Ciconiiformes the tendency is for 

 the first to become very long and secondarily twisted up with the 

 duodenal looj), the second and third becoming nearly obliterated. 

 In the Ardeiformes the first and second are generally rather long 

 and definite and may form minor loops, the third is often reduced 

 to a little bunch of small loops closely set together. In Balceniceps 

 the three loops are i-ather more distinct than in either the Storks 

 or the Herons, remaining in the more generalized Steganopod con- 

 dition, but such difterentiation as exists approaches the Ardeine 

 pattern and shows no trace of the Ciconine peculiarities. 



In the assemblage Meckel's diverticuluin is actually or very 

 nearly at the extremity of the axial loop of the tract. When it 

 is not quite terminal, it is always on the proximal side of the 

 loop and is then bent pai"allel with it, the free tip pointing 

 proximally. The axial loop may grow out to a great relative 

 length. These dispositions are distributed very irregularly 

 throughout the whole assemblage Avhich I am discussing. The 

 axial loop, for instance, is long and has the diverticulum at the tip 

 in some Storks and in many of the smaller Eagles and Falcons. 

 It is short, but usually has the diverticulum at the tip in some 

 of the Herons and in Scoptts, Cathartes and Polyhorus. It is 

 short and bears the diverticvilum proximal to its apex in Phaethon^ 

 Pelecanus, Fregata, Pseudotantalus, Serpentarixis and Neophron. 

 The latter condition exists in Balceniceps, and it is plain that its 

 occurrence has no systematic significance. 



In the Pelargomorphine Legion the distal part of Meckel's tract 

 is less highly differentiated, and therefore affords fewer dis- 

 criminating characters. The portion of it that follows Meckel's 

 diverticulum is usually thrown into a bunch of short, irregular 

 loops, and then follows a well-marked supra-duodenal looj^, 

 supplied from the mesenteric vein, and one or more definite 

 supra-csecal kinks. In Balcenicej^s, there is first the irregular 

 region, then a definite short loop, then a long typical supra- 



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