■2i0 BR. P. CHALMERS MITCHELL ON THE 



Ei'om the point of view of couforniation of the iutestiual tract, it does not a])peai' that 

 the Pteroclo-Columbae stand in close relation to other Charadriiforni birds. The only 

 character in common is the tendency for Meckel's tract to be drawn out into long minor 

 loops, and tlie particular apocentrieity which reaches its climax in the elaborate spiral of 

 the axial loop of Pigeons is different from that in the specialized Charadriid:e such as 

 llecurvh'Ofttra and Scolopax, the difference being made plain by the relative positions of 

 Meckel's diverticulum. The comparison with Opisfhocomus seems to give a more fertile 

 suggestion. 



Summary op the Alectoeomorphine Legion. (Plate 22.) 



Gadow unites the Tinamiformes, Galliformes, Gruiforines, and Charadriiformes into 

 the Alectoromorpha3, the first Legion of his second Brigade, and I 2)ropose now to review 

 shortly the characters of the intestinal tract j^resented in this large assemblage. It must 

 be clear that the conformations of the gut within this group do not follow many of the 

 more generally accepted modes of subdividing the group so readily and naturally as in 

 the case of the Pelargo-Colymbomorphine Brigade. Those, I tliiuk, who have paid most 

 attention to the classification of birds will he prepai-ed for this result, for the many and 

 different divisions proposed suggest that the assemblage is still in indifferent order. 

 Prom the pohit of view of the subject of this Memoir, it is in the first place clear that 

 the Turnices and Galli stand apart from the other gronj^s, inasmuch as their pattern of 

 intestinal tract has remained markedly archecentric, differing extremely little from that 

 in Palamedea. Next, the Tinamidse retain no suggestion of Struthious affinity ; they 

 have moved ftir apocentrically, while the Batites, like the Galli, have remained close to 

 the archecentric condition. The Tinamidaj present on the one hand most striking 

 resemblances witli the Otididue, an apocentric type of the Gritiformes. On tlie other 

 baud, the radius of apocentrieity on which they lie suggests that of Opisthocornus, 

 Pterocles, and the Columbse. Opisthocornus, one of the Galliformes of Gadow, certainly 

 stands far apart from the others, and, so far as the gut is concerned, an affinity with 

 Pterocles and the Columbae is most clearly indicated. The guts of Columba3 and of 

 Pterocles are extremely similar, and there is no indication of any alfinity Avith the 

 conformations exhibited in the other Charadriiformes or Gruiformes. 



The Galli, Turnices, Oplsthocomm, and Pteroclo-Columba' having been disposed of, 

 there is less difficulty in arranging the confontiations of the gut in other members 

 of the Alectoromorphine Legion in coherent order. A conformation that is a simple 

 derivative of tlie archecentric form appears to underlie all of them, and this may be 

 called a Liraicoline-Gruiform metacentre. The duodenum is simple ; Meckel's tract is 

 slightly elongated, but the elongation is proximad of the diverticulum so that that 

 appears on the distal limb of an axial loop. The distal region of Meckel's tract shows 

 the beginning of separation into a definite supra-duodenal loop to which the long caeca 

 are attached, and into a loop between that and the diverticulum. The rectum is short 

 and straight. Tlie simpler Limicoline families, such as the ChionidtE, Glareolida', 

 Tliinocoridoe, and Parridse, are extremely close to this Limicoline-Gruiform metacentre; 

 and the Lari, which from this point of view present no clear distinction into Alcidai and 



