ANATOMY OF VERTEBRATES. 189 



those characters of the clavicle of lizards. Accordingly in the 

 progressive reduction of the pelvic arch to a single hremapophysial 

 element sustaining the appendage, as in Osseous Fishes, we may 

 discern the characters of the ' ischium ' in that element, rather 

 than of the pubis. 



The ilium of the Crocodile is twice as broad as long, produced 

 beyond the two vertebrae to which it is articulated : it descends 

 vertically to the acetabulum, of which it forms the upper half. 

 The anterior production or tuberosity, a, is the thickest, the pos- 

 terior is the longest. The ischium developes a strong bent process 

 from the fore part of the acetabular end, to which the pubis is 

 articulated : as it descends and inclines inward, it becomes flat- 

 tened and expanded, b, and joins its fellow by a moderately 

 extended ischial symphysis. The pubis is directed more forward, 

 and though smaller and more slender, resembles the ischium by 

 the expanse of the medial end. As ossification is not extended 

 along the mid-line from the ischial symphysis to the pubis, no 

 ' obturator foramina ' are defined, but a wide vacuity intervenes, as 

 in Chelone and Trionyx. 



The femur, fig. 57, v, is bent in curves opposite to those of the 

 humerus : the head is convex, subcompressed laterally, flattened 

 externally : the chief process is from the inner side, at the upper 

 third of the shaft : there is a ridge external and above this process: 

 the distal end expands transversely, and developes backward two 

 condyles ; the outermost receives part of the head of the fibula. It 

 is longer than the humerus, but in a less degree in modern than in 

 mesozoic crocodiles. The tibia, figs. 57 and 120, 66, presents a 

 large triangular head to the femur, the division of the back part of 

 which into two condyles is feebly indicated : it offers a smaller 

 convex crescentic surface to the tarsus. The fibula, ib. 67, is 

 slender and subcylindrical ; much compressed above, more ex- 

 panded and triangular below. Each of the foregoing long bones 

 has a medullary cavity. There is no patella ; but there is a fibro- 

 cartilaginous ' fabella,' with granular bone, in old crocodiles, 

 behind the outer condyle. 



The principal tarsal bone, fig. 120, c, represents the astragalus, 

 naviculare, and entocuneiform, connate, of the human series; 

 articulating with the distal end of the tibia and a small part of the 

 fibula above, with the calcaneum and cuboid externally, and with 

 the first and second metatarsals and the ectocuneiform below. 

 The calcaneum, d, intervenes between the fibula and cuboid, and 

 has a short but thick posterior tuberosity, y, fig. 57. The cuboid, 

 fig. 120, e, supports the fifth, v, fourth, iv, and part of the third, 



