The femur is gradually expanded to the extremities. Proximally there is a trochanteric ala, besides the obtuse head. Distally the condyles are well distinguished, the external or fibular being truncate. The fibula is less than three-fifths the length of the femur, and is expanded at both extremities. Two proximal tarsals are distinct; the one next the fibula is larger than the other and transverse suboval in form. It has a median dividing ridge as though composed of fibulare and intermedium coössified. The tibiale is subtriangular. There are five distinct phalangeal tarsals. The toes are, in the order of their lengths, beginning with the shortest, 1-2-5-3-4. Their phalanges (including metatarsals) are, in the proper order, commencing with the hallux, 3-3-4-5?-5, the distal end of the fourth finger being lost. These bones are rather stout, and the unguals are simply conic. The form of the foot is short and wide. The number of the phalanges is nearly similar to that found in _Amphibamus grandiceps_, excepting that in that species the fifth digit has but 4. They are more numerous on most of the digits in _Sauropleura digitata_. Cope (Trans. Am. Phil. Soc., XVI, 289, fig. 1, 1888) contributed the following note on _Ichthycanthus platypus_: "A reëxamination of the type specimen of this species from the Coal Measures of Ohio, preserved in the Museum of Columbia College, New York, enables me to refer this species to the Rachitomi. The neural spines are distinct, showing that it belongs, probably, to the Eryopidæ. As the skull is not preserved, I can not determine the genus positively, but refer it for the present to Eryops. I append a figure of the posterior foot, which displays the characters of the tarsus of this group for the first time. The number of tarsals is as in a Theromorph reptile, except that two elements represent the cuboid bone as in the reptile, _Stereosternum tumidum_ Cope; giving five elements in the distal tarsal row. There is but one centrale and no intermedium. Two fragments of caudal vertebræ adhere to the specimen." Measurements of Ichthycanthus platypus Cope. mm. Length of 10 dorsal vertebræ 45 Length of 15 caudal vertebræ 55 Length of centrum of a dorsal 3.8 Total elevation of a posterior dorsal 14 Length of femur 32 Length of first digit 10 Diameter of femur medially 4.5 Diameter of femur distally 8.3 Length of fibula 18 Diameter of fibula proximally 7 Width of sole at second row of tarsal bones 17 Length of foot to end of third digit 31 Length of third digit 22 Length of fifth digit 20 The writer has had the privilege of restudying this interesting specimen and has already (484) described the foot and tarsus, as follows: