O. C. Marsh—On Dinosaurian Reptiles. 493 
Each sacral rib supported by two vertebra; diapophyses dis- 
tinct from sacral ribs. Sternum unossified. Pubes projecting 
downward, and united distally. Fore limbs small; limb bones 
hollow; feet digitigrade; digits with prehensile claws; loco- 
motion mainly bipedal. 
(1) Family degalosauride. Lower jaws with teeth in 
front. Anterior vertebrae convexu-concave; remaining verte- 
bree biconcave ; five sacral vertebree. [lium expanded in front 
of acetabulum; pubes slender. Femur longer than tibia. 
Astragalus with ascending process. Five digits in manus and 
four in pes. 
Genus Megalosaurus (Poikilopleuron). Jurassic and Cre- 
taceous. Known forms European. 
(2) Family Dryptosauride. Lower jaws with teeth in 
front. Cervical vertebrae opisthoccelian ; remaining vertebree 
biconcave ; sacral vertebree less than five; ilium expanded in 
front of acetabulum ; distal ends of pubes codssified and much 
expanded; an interpubic bone. Femur longer than tibia; 
astragalus with ascending process. Fore limbs very small, 
with compressed prehensile claws. 
Genera Dryptosaurus (Lelaps), Allosaurus, Colosaurus, 
Creosaurus. Jurassic and Cretaceous. All from North 
America. 
(3) Family Labrosauride. Lower jaws edentulous in front. 
Cervical and dorsal vertebrze convexo-coneave; centra cav- 
ernous or hollow. Pubes slender, with anterior margins 
united ; an interpubic bone. Femur longer than tibia; astrag- 
alus with ascending process. 
Genus Labrosaurus. Jurassic, North America. 
(4) Family Plateosauride (Zanclodontide). Vertebre bi- 
concave; two sacral vertebre. Ilium expanded behind 
acetabulum; pubes broad, elongate plates, with anterior mar- 
gins united; no interpubic bone. Femur longer than tibia; 
astragalus without ascending process. Five digits in manus 
and pes. 
Genera Plateosaurus (Zanclodon),? Teratosaurus, Dimodo- 
saurus. Triassic. Known forms European. 
(5) Family Anchisauridw. Skull light in structure, with 
recurved, cutting teeth. Vertebree biconcave. Bones hollow. 
Ilium expanded behind acetabulum; pubes rod-like and not 
eodssified distally; no interpubic bone. Fore limbs well 
developed. Femur longer than tibia. Five digits in manus 
and four in pes. (See Plate X, figure 1.) 
Genera Anchisaurus (Megadactylus), Ammosaurus, ? Arcto- 
saurus, Bathygnathus, and Clepsysaurus, in North America; 
and in Europe, Palwosaurus, Lhecodontosaurus. All known 
forms Triassic. 
