SHUPELDT : OSTEOLOGY OF THE STEGANOPODES 



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(1899) retains all the Anhingas in the family Plotidse, and, in addition to two fossil 

 forms, recognizes our existing species, viz : P. rufus, P. melanog aster, P. novse- 

 hoUandise, and P. anhinga. The Anhinga anhinga is the sole representative of this 

 family in the United States. A peculiarity of the skeleton of Anhinga is, it is 

 almost completely non-pneumatic. It is only into the base of the cranium and the 

 articular ends of the mandible that air gains access through minute foramina occu- 

 pying the usual sites. 



Of the Skull. — This bird has a very perfect " cranio-facial hinge," and measuring 

 each way from the center of it we find the superior mandible to be about 1.5 cm. 

 longer than the cranium. In form the superior mandible is long, narrow and spear- 

 shaped, being drawn out to a sharp point. It is nearly straight. Beneath, it is flat 

 with cultrate tomia. The culmen is rounded off, and the nasals have so fused with 

 the surrounding bones of the face that most of the sutural lines cannot be dis- 

 tinguished in the adult. Where the external nostrils would naturally occur, there 

 are usually present only minute holes that do not appear to reach in so far as the 

 rhinal chamber. Viewed from above, we are to observe that the cranial and frontal 



sr.iii/. 



Fig. 3. Left lateral view of the skull, including mandible, of a specimen of Anhinga anhinga. Natural size in 

 outline, by the author from specimen 18259 of the CoU.U. S. Nat. Museum, sr.in, the supramaxillary bone. 

 Fig. 4. The same skull, seen from above. Mandible removed. 



region are somewhat narrow and elongated ; the former being smooth and moder- 

 ately rounded, the latter flat and measuring about half a centimeter between the 

 sharp edges of the superior peripheries of the orbits. For its hinder half, longi- 

 tudinally, this part of the skull presents a low, median prominence, created by the 

 approach upon either side, of the extensive, though shallow, crotaphyte fossa. We 



