170 



PELVIS. 



of the Tiger and some Carnivora, and which 

 has an evident relation to the increase of 

 leverage for the muscular power of adduction 

 required to grasp their prey, as also has 

 the convergent direction of the ischia just 

 mentioned. The pubes (d) are long, and are 

 like the ischia, less directed backwards, form- 

 ing an ilio-pubic angle of 125 in the Eagle 

 and 140 in the Owl. They have a great 

 inward convergence in most Vultures and 

 Falcons, and in the Hen Harrier and brown 

 Eagle are closely approximated in the median 

 line and connected by ligaments in a sort of 

 short symphysis ; generally the ischia and 

 pubes unite posteriorly to enclose a small 

 obturator foramen in the Diurnal birds of 

 prey. In some Falcons and Vultures, how- 

 ever, according to Carus, they are united in 

 their whole extent ; while, in the Owls, this 

 union does not take place at all. 



The Reptile pelves present some specimens 

 which approach the Mammalian type, in the 

 formation of a perfect pelvic girdle by inter- 

 pubic and inter-ischial symphysis. In these 

 animals, however, the three components of 

 the innominate bones remain separate through- 

 out life, and are connected in the acetabula 

 by ligament only. The manner of articula- 

 tion of the ilia with the sacrum is also cha- 

 racteristic. We have seen that in Mammals 

 this connection of the ilia takes place about 

 the centre or at the anterior half; and in 

 Birds by the whole length of the alae. In 

 "Reptiles it takes place by the tip only of the 

 upper extremity of the ilia, giving much less 

 strength, but far greater mobility to these 

 bones. In the Chelonian and Saurian reptiles 

 also, the ilia are directed forwards and down- 

 wards instead of backwards and downwards, as 

 in Birds and Mammals, and thus the axis of 

 the anterior pelvic outlet is directed upwards 

 and forwards, and the lumbar vertebras, instead 

 of the coccygeal, form part of the posterior 

 pelvic wall. The pelvic bones are simple, 

 and the sacro-sciatic notch can hardly be said 

 to exist. 



In the Ophidians and some Saurians the 

 pelvis, like the corresponding extremities, is 

 totally wanting. 



In the Chelonia, the fresh-water, and the mud 

 Tortoise, or Trionyx, have a sacrum composed 

 of three pieces, soldered, like the dorsal ver- 

 tebrae, to the back-plate. Their long transverse 

 processes project from it, and unite in a tuber.- 

 cle at their apices, to which the ilia are attached. 

 The caudal vertebras are numerous. 



The ilia(fis>. 108. a.} are short, thick, curved 

 roundish and clubbed inferiorly, and are di- 

 rected outwards, forwards, and downwards, 

 extending under the back plate directly be- 

 tween the sacrum (at i) and the acetabula. In 

 the Tortoise and Trionyx they are moveable 

 upon the sacrum forwards and backwards. 

 From the acetabula, the ischia (c), larger than 

 the ilia, pass, almost at a right angle, backwards 

 and inwards, and unite in a median symphysis 

 (rf), forming the real pelvic circle, and present- 

 ing a sharp angle posteriorly in the Trionyx 



(/) and fresh-water Turtle. In the land and 

 fresh- water Tortoise this symphysis is continu- 

 ous anteriorly with the inter-pubic (e), forming 

 with it a cross-shaped suture, and the ob- 

 turator foramen on each side is distinct and 

 separate ; but, in the Turtle and Trionyx, as in 

 most reptiles, the inter-pubic and inter- ischi- 

 atic symphyses are separated and connected 

 by cartilage only, and thus, in the dry bones, 

 the obturator foramina are coalesced in one 

 large opening, and the pubes and ischia have 

 the appearance of large ribs connected at their 

 ventral extremities. The pubes (A) are the 



Fig. 108. 



9 f 



Pelvis of the Trionyx, or Mud Tortoise, superior 

 view. 



largest of the bones in the reptile pelvis, and, 

 as seen in the Turtle, pass each from the 

 acetabula as a thick bone, which expands as 

 it passes downwards into a broad plate, and 

 divides into an inner portion which unites 

 with its opposite fellow in a symphysis (e, e'} 

 and an outer portion, free and directed ex- 

 ternally (h). In the Chelydes all the pelvic 

 bones are ankylosed to the plastrum or to the 

 back-plate ; but in the others, the ischia and 

 pubes are connected to the plastrum by liga- 

 ments only. The anterior pelvic opening in 

 the Chelonia is directed upwards and forwards. 



The pelvis of the fossil Plesiosaurus is very 

 like that of the Tortoise, with narrow, small, 

 and weak ilia, with the fan-like, spreading 

 ischia, and large square pubes uniting in 

 a common symphysis, by a crucial suture. 

 The pelvic and shoulder bones have a great 

 resemblance in the Chelonian as well as in 

 the Saurian reptiles. 



Of the Saurian reptiles the Crocodiles have 

 two sacral vertebras with large spines (Jig. 109. 

 a, a'), which support the ilia by strong prismatic 

 apophyses, ankylosed together at the ends, and 

 separated by a suture, in the young animals, 

 from the bodies of their vertebras. The caudal 

 bones in all the Saurians, are very numerous. 



The ilia (b) are very short, and in some 

 species almost cuboid', slightly bent, with an 

 inward concavity, and directed downwards 

 and a little forwards, but almost at right 

 angles to the spine, with the superior angle 

 (e) projecting backwards. The ischia (c) 

 are long, and directed, like the sides of an 



