158 FIELD COLUMBIAN MusEUM—GEOLOGY, VOL. II. 
young of P. zmgens, as is not likely, then we have at least three distinctly 
different species of the genus, perhaps a fourth in P. comptus. 
A much more interesting question is: What relation do the genera, 
Nyctosaurus, Ornithochetrus, and Pteranodon (Ornithostoma) bear to each 
other and to Prerodactylus ? 
The classification which has hitherto seemed the best to display the 
relationship of these forms is the following : 
Suborder Pterodactyloidea. Tail short; wing metacarpal, at least as 
long as the bones of the antebrachium; fifth digit of pes vestigial, with- 
out phalanges. } 
Family Pterodactylidae. Scapula not articulating with supraneural 
facet. 
Genus Prerodactylus. Teeth present. 
Genus JVyctosaurus. No teeth. 
Family Ornithocheiride. Scapula with an articular facet united with 
neural facet of the notarium. 
Genus Ornitkocheirus. Jaws with teeth. 
Genus Preranodon (Ornithostoma). Jaws without teeth. 
However, a better knowledge of the genus /Vycfosaurus. convinces 
me that its relationship is closer with Ornithochetrus than with Pterodacty- 
Jus; that it has gone much further in specialization in the same direction 
with Orntthochetrus and Pteranodon. Very little now remains to be 
known of the osteology of both these genera, and not much of Oraz- 
thochetrus. Their characters as a group may be summed up as follows. 
While some parts of the skeleton of Orzzthochetrus are yet unknown, I 
am confident that future discovery will produce nothing very discrepant. 
Ornithocheiride. Head elongate, slender; no antorbital vacuity; 
internal nares large; eight cervical, ten dorsal (¢eranodon?), six 
sacral, and ten to twelve caudal vertebrz present, the last dorsal co-os- 
sified with the sacrum; first three or four dorsal vertebree united into a 
notarium, with stout, anchylosed ribs articulating with the sternum; pos- 
terior dorsal ribs very slender, single-headed, and nearly straight; three 
or four pairs of flattened V-shaped ventral ribs present. Ilium much 
elongated; ischio-pubis with an obturator foramen; prepubes band-like, 
co-ossified, with an anterior, flattened projection on each side. Coraco- 
scapula with only a slight projection below the glenoid cavity, co-ossified 
in the adult; scapula but little longer than the coracoid, not narrowed 
distally. Three carpals present; forearm much longer than humerus; third 
and fourth metacarpals very short, pointed proximally, not articulating 
with carpus; second metacarpal thread-like proximally; fifth metacarpal 
