172 THE COAL MEASURES AMPHIBIA OF NORTH AMERICA. 



the chevron bones. They are much reduced on the eighteenth caudal vertebra, 

 where the chevron bones are considerably longer. 



The abdominal rods are quite slender. The hind limb is quite stout for this 

 order. The femur is regularly expanded at both extremities, but the distal is deeply 

 and openly grooved, distinguishing the condyles, while the proximal end is plane. 

 There is no trochanter visible. The ulna and radius are well separated, and are 

 three-fifths the length of the femur. There is a large fibular tarsal bone of a sub- 

 quadrate outline. In immediate contact with it is probably the external digit with 

 5 phalanges or segments ; the ungual is simply conic. The femur is as long as 5 dorsal 

 vertebrae. The ribs have expanded, undivided heads, and extend to the abdominal 

 armature. 



MEASUREMENTS OF THE TYPE OF ICHTHYCANTHUS OHIENSIS COPE. 



mm. mm, 



Length of last 10 dorsal vertebrae 47 Proximal diameter of femur 8 



Length of first 23 caudal vertebrae 117 Width of lower leg 9 



Length of a posterior rib 29 Length of fibula 15 



Length of a posterior dorsal vertebra 5 Length of tarsal bone 6 



Length of twenty-second caudal vertebra. 5 Length of digit 27 



Length of femur 25 



Ichthycanthus platypus Cope. 



COPE, Proc. Am. Phil. Soc., pp. 574, 575, 1877. 



COPE, Trans. Am. Phil. Soc., xyi, p. 289, fig. i, 1888. 



BAUR, Beitrage zur Morphogenie des Carpus und Tarsus der Vertcbratcn, i Thc-il, p. 16, 1888. 



MOODIE, Science, n.s., XLI, No. 1044, p. 34, 1915. 



MOODIE, Am. Jour. Sci., xxxix, pp. 509-512, fig. 2, 1915. 



Type: Specimen No. 7954 G, and obverse, Department of Geology, Columbia 

 University. (Plate 23, fig. i.) 



Horizon and locality: Linton, Ohio, Coal Measures. 



This amphibian is represented by the same portions of the skeleton as the preced- 

 ing species, furnishing a good basis for comparison. It is very well preserved, display- 

 ing the characters, especially of the hind foot, which is almost entirely represented. 



Several features distinguish it from the /. ohiensis, one of which is of more than 

 usual value if correctly indicated by the fossil. There are 10 vertebras from the 

 anterior end to the sacrum preserved in place, and none of them supports a rib, 

 nor are there any ribs visible anywhere on the block of shale. I suspect that they 

 exist on more anterior vertebrae, or may have been displaced to a more anterior 

 position than they normally occupy. The abdominal chevrons are more anterior in 

 position than are those of the I. ohiensis. The hind legs are longer than in that 

 species; in this one the femur equals 7.5 vertebral centra in length. The external 

 digit, on the other hand, while bearing 5 phalanges, is distinctly shorter. The 

 fibular tarsal is of a transverse oval, not quadrate, form. 



The dorsal centra are shorter and deeper than long; the neural arches are ele- 

 vated, with short but distinct zygapophyses, and a flat, subquadrate, superiorly 

 truncate, neural spine. They bear short, vertically compressed diapophyses near the 

 base of the arches . The neural spines of the caudal vertebrae become rapidly more slen- 

 der, and also diminish in length, while the zygapophyses are continued to the fifteenth 

 vertebra. The chevron bones are slender, and inclose a moderate haemal opening. 



The femur is gradually expanded to the extremities. Proximally there is a tro- 

 chanteric ala, besides the obtuse head. Distally the condyles are well distinguished, 



