mm. Length of interclavicle 71.5 Greatest width 78 Width of lateral concavity 39 [Illustration: Fig. 37.--So-called interclavicle of _Eurythorax sublævis_ Cope. (_Sagenodus._) No. 75. (After Cope.)] CHAPTER XXII. THE MICROSAURIAN FAMILY ICHTHYCANTHIDÆ, FROM THE COAL MEASURES OF OHIO. =Family ICHTHYCANTHIDÆ new family.= This family is the most recently recognized group of the Linton fauna. Its members, of which there are two known species, are distinct from all other Coal Measures Amphibia in the possession of an osseous tarsus (483, 484), with its associated reptile-like limb bones. There are preserved fine scutellæ in a large patch near the vertebral column. The vertebral spines are broad and heavy, with the vertebral centra amphicœlous. =Genus ICHTHYCANTHUS Cope, 1877.= Cope, Proc. Am. Phil. Soc., p. 573, Feb. 3, 1877 (Pal. Bull. 24). Baur, Beiträge zur Morphogenie des Carpus und Tarsus der Vertebraten, I Theil, p. 16, 1888. Cope, Trans. Am. Phil. Soc., XVI, p. 289, fig. 1, 1888. Moodie, Science, n. s., XLI, No. 1044, p. 34, 1915. Moodie, Am. Jour. Sci., XXXIX, pp. 509-512, fig. 2, May, 1915. Type: _Ichthycanthus ohiensis_ Cope. The generic characters are derived from the characters presented by the posterior dorsal and caudal vertebræ, with adjacent parts. The posterior limbs are well developed, with distinct tibia and fibula, osseous tarsus, and 5 digits. Ribs elongate, simple, curved. Abdominal armature consisting of bristle-like rods in anteriorly directed chevrons. Dorsal vertebræ not elongate, with simple neural spines. Tail large, its vertebræ ossified, and furnished with slender chevron bones which terminate in a hæmal spine. Neural spines broad and directed backwards; the caudal series somewhat resembling that of a fish. All the centra are amphicœlous. This genus differs from all those with enlarged and sculptured neural spines, and from those with abdominal scutes. It is equally distinct from those without ribs, abdominal rods, or limbs. It is possible that some of the species referred to _Tuditanus_, in which these parts are unknown, may belong to it, or that it may be established on a small species of _Leptophractus_, a genus known only as yet from the skull. With our present imperfect knowledge of the Linton forms it seems best to refer _I. ohiensis_ and _I. platypus_ to this distinct genus, _Ichthycanthus_. =Ichthycanthus ohiensis Cope.= Cope, Proc. Am. Phil. Soc., 1877, p. 573 (Pal. Bull. 24). Type: Specimen in the American Museum of Natural History. Horizon and locality: Linton, Ohio, Coal Measures. Collected by Dr. J. S. Newberry, in the summer of 1876.