mm. Entire length of fossil 98 Length of skull 22 Width across base of skull 28 Long diameter of eye 10.5 Transverse diameter of eye 8 Interorbital space 4 Length of mandible 26 Depth of mandible at coronoidal region 3.5 Depth of dentary 2 Length of long tooth 2 Diameter of long tooth at base .5 Length of preserved portion of vertebral column 64 Length of a centrum 3 Median width of a centrum 1.5 Length of rib 6.5 Width of rib at base .33 Length of coracoid 5 Width of coracoid at anterior end 2.5 Length of carpal space 5 Length of humerus 18 Width of shaft 1 Distal width of humerus 4 Length of radius and ulna 10.5 Length of metacarpal 6 Length of ventral armature preserved 24 Number of rods in length of 5 mm 10 [Illustration: MOODIE PLATE 19 Type specimen of _Ctenerpeton alveolatum_ Cope, from the Coal Measures of Ohio. × 1.33. Original in U. S. National Museum.] [Illustration: MOODIE PLATE 20 1. Skull of _Erpetosaurus minutus_ Moodie, from the Cannelton slates of Pennsylvania. Original in U. S. National Museum. Enlarged × 3.3. 2. Skull and anterior part of body of _Ptyonius pectinatus_ Cope, from the Coal Measures of Linton, Ohio. Original in U. S. National Museum. × 1. 3. Skeleton of Eosauravus copei Williston, from the Coal Measures of Linton. Ohio. "The oldest known reptile from North America" and closely related structurally to the Microsauria. Original in U. S. National Museum. × 1. 4. Part of the ventral scutellation and ribs of Sauropleura digitata Cope, from the Coal Measures of Linton. Ohio. Original in American Museum of Natural History. × 1. ] CHAPTER XVIII. THE MICROSAURIAN FAMILY NYRANIIDÆ, FROM THE COAL MEASURES OF OHIO. =Family NYRANIIDÆ Lydekker, 1890.= Lydekker, Cat. Fossil Reptilia and Amphibia, p. 166, 1890.