Miscellaneous. 233 



On a new Subclass of Fossil Birds (Odontornithes). 

 By 0. C. Marsh. 



The remarkable extinct birds with biconcave vertebra? (Ichthyor- 

 nidae), recently described by the writer from the upper Cretaceous shale 

 of Kansas *, prove on further investigation to possess some additional 

 characters, which separate them still more widely from all known 

 recent and fossil forms. The type species of this group, IcJuhyornis 

 dispar, Marsh, had well-developed teeth in both Jmvs. These teeth 

 were quite numerous and implanted in distinct sockets ; they were 

 small, compressed, and pointed, and all of those preserved 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 equally nume- 

 rous, and essentially the same as those in the mandible. 



The skull was of moderate size, and the eyes were placed well 

 forward. The lower jaws are long and slender, and the rami were 

 not closely united at the symphysis ; they are abruptly truncated 

 just behind the articulation for the quadi-ate. 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 

 were large in proportion to tlie legs ; and the humerus had an extended 

 radial crest. The metacarpals arc united, as in ordinary birds. The 

 bones of the posterior extremities resemble those in swimming birds. 

 The vertebrae were all biconcave, the concavities at each end of the 

 centra being distinct and nearly alike. Whether the tail was elon- 

 gated cannot at present be determined ; but the last vertebra of the 

 sacrum was unusuaUy large. 



This bird was fully adult, and about as large as a pigeon. "With 

 the exception of the skuU, 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 portions 

 of lower jaws found with them were regarded by the writer as repti- 

 lian t ; the possibility of tlieir forming part of the same skeleton, 

 although cojisidered at the time, was not deemed sufficiently strong 

 to be placed on record. On subse(}uently removing the surrounding 

 shale, the skull and additional portions of both jaws were brought to 

 light, so that tliere cannot now be a reasonable doubt that all are 

 parts of the same bird. The possession of teeth and biconcave ver- 

 tebrae, although the rest of the skeleton is entirely avian in type, 

 obviously implies that these remains cannot be placed in the present 



* Amer. Joiu-n. of Sci. and Arts, vol. iv. p. .'544, Oct. 1872, and vol. v. 

 p. 74, .Ian. 1873. 'Annals,' Jan. 1873, p. 80. 

 t Amer. Journ. of Sci. and Arts, vol. iv. p. 400, Nov. 1872. 



