THE OOLOGIST 



175 



The two groups of Cretaceous birds 

 are represented by Hesperornis and 

 Ichthyornis. Hesperornis was large 

 and flightless, specialized for diving. 

 The wings were abortive, a single 

 bone remaining of a wing which once 

 was suitable for flying, and necessarily 

 implies that following their evolution- 

 ary development the wings passed 

 through a long period of degeneration. 

 The legs were powerfully constructed, 

 and were unique in that they extended 

 at right angles from the body, much 

 as oars protrude from a row boat. This 

 arrangement together with the highly 

 developed swimming feet denotes in- 

 tense specialization. In accord with 

 the limb development was the elongat- 

 ed head and body. It seems impos- 

 sible that these birds could walk upon 

 land, but it has been suggested that 

 the vertebrae were so articulated that 

 the bird could flounder over the 

 ground much in the manner of a seal. 

 The tail consisted of twelve vertebrae, 

 the last four being joined together in 

 a terminal mass. It was articulate In 

 a vertical plane and was probably 

 used as an elevating rudder or as a 

 paddle in swimming. Hesperornis had 

 sharp pointed teeth set in a continu- 

 ous groove. The interior portion of 

 the upper jaw was without teefh, and 

 was likely provided with a horny 

 covering as in modern birds. Hesper- 

 ornis was truly a formidable creature, 

 often attaining a length of six feel, 

 and it doubtless wrought havoc among 

 the fishes upon which it preyed. 



Ichthyornis contrasted greatly with 

 Hesperornis. While both were aquatic, 

 Ichthyornis was about equal in 

 size to a rock pigeon. Its teeth were 

 comparatively large, and set in dis- 

 tinct sockets twenty to each jaw, and 

 were directed obliquely backward. The 

 rami of the mandibles were loosely 

 united, and it is probable that the 

 jaws were not sheathed in horn. This 

 arrangement of the teeth in sockets, 



together with the amphoeoelus Verte- 

 brae (similar to those in fishes, hence 

 the name Ichthyornis — fish bird) are 

 distinct reptilian characteristics, as 

 primitive as those of Archaeopteryx. 

 Unlike Hesperornis the sternum was 

 well developed, and the wings adapted 

 for flight. 



These two birds living 95,000,000 

 years ago were further apart than any 

 two species living today (Marsh), and 

 yet they had a common ancestor in 

 Archaeopteryx 100,000,000 years be- 

 fore. 



William Drumm Johnston, Jr. 

 The University of Cincinnati. 

 Bibliography 



1. Stromer von Reichenbach: Lehr- 



buch der Palaozoologie, 11. Leip- 

 zig, 1912. 



2. Alleyne Nicholson and Richard 

 Lydekker, Manual of Palaeontol- 

 ogy, Vol. II, Edinburgh. 



3. Fredrick A. Lucas, Animals of the 

 Past, American Museum of Natural 

 History, Handbook. New York. 



"CAROLINA WREN BUILDING MA- 

 TERIAL" 



Rowing from tree to tree out in our 

 Municipal lake. We covered lots of 

 the over-flowered parts of the lake ob- 

 serving nesting cavities of Wrens, 

 Owls, Chickadee, Woodpeckers, and 

 Tufted Titmouse. 



Among our most noticed discovery 

 for the day was a Carolina Wren's nest 

 with three eggs. Wren on nest, which 

 was composed of several different 

 kinds of grasses, half a dozen different 

 kinds of leaves, several feathers 

 among which was a Barred Owls 

 feather. Some green moss, horse hair, 

 a snake skin, a few sticks, and twigs. 

 Lined with grass blades and hair from 

 horse mane. In a dead elm, one- 

 fourth mile from shore, 5 feet up, 

 cavity facing the north, large en- 



