116 GEOLOGY. 
recently described by the writer from the upper Cretaceous shale 
of Kansas,* prove on further investigation to possess some ad- 
ditional characters, which separate them still more widely from all 
known recent and fossil forms. The type species of this group, 
Ichthyornis dispar Marsh, has well developed teeth in both jaws. 
These teeth are quite numerous, and implanted in distinct sockets. 
They are small, compressed and pointed, and all of those pre- 
served are similar. Those in the lower jaws number about twenty 
in each ramus, and are all more or less inclined backward. The 
series extends over the entire upper margin of the dentary bone, 
the front tooth being very near the extremity. The maxillary 
teeth appear to have been aid numerous, and essentially the 
same as those in the mandi 
The skull is of moderate size, and the eyes placed well forward. 
The lower jaws are long and slender, and the rami are not closely 
united at the symphysis. They are abruptly truncated just behind 
the articulation for the quadrate. This extremity, and especially 
its articulation, is very similar to that in some recent aquatic 
. 
birds. The jaws were apparently not encased in a horny sheath. 
The scapular arch, and the bones of the wings and legs, all 
conform closely to the true ornithic type. The sternum has a 
prominent keel, and elongated grooves for the expanded coracoids. 
The wings are large in proportion to the legs, and the humerus 
has an extended radial crest. The metacarpals are united, as in 
ordinary birds. The bones of the posterior extremities resemble 
those in swimming birds. The vertebrie are all biconcave, the 
concavities at each end of the centra being distinct, and nearly 
ike. Whether the tail was elongated cannot at present be deter- 
mined, but the last vertebra of the sacrum is unusually large. 
This bird was fully adult, and about as large asa pigeon. With 
the exception of the skull, the bones do not appear to have been 
pneumatic, although most of them are hollow. The species was 
carnivorous and probably aquatic. 
When the remains of this species were first described, the por- 
tions of lower jaws found with them were regarded by the writer 
as Reptilian; the possibility of their forming part of the same 
skeleton, although considered at the time, was not deemed suf- 
ficiently strong to be placed on record. On subsequently removing 
the surrounding shale, the skull and additional portions of both 
* American Journal Science Arts, vol. iv, p. 344, Oct. 1872, and vol. v, p. 74, Jan., 1873. 
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