PELVIS. 



171 



isosceles triangle, downwards and inwards, 

 uniting in a median symphysis (/), and much 

 resemble the coracoid bones of the shoulder. 

 The acetabula of the crocodile look di- 

 rectly outwards, have strong inter-articular 

 ligaments, and are formed only by the ilia 

 and ischia, the latter presenting, just below 

 the acetabulum, anterior apophyses which 

 support the pubes. The pubes (d) are directed 

 much forwards, downwards, and towards each 

 other, but do not touch in the median line, 

 being united only by the abdominal aponeu- 



Fig. 109. 



n 



Pelvis of the Gangetic Crocodile (side view). 



rosis (A). They are connected by the anterior 

 border with the posterior abdominal ribs (g). 



The Lizards have, like the crocodiles, two 

 sacral bones, as in the Iguana and Great 

 Monitor. In many Lizards the sacral trans- 

 verse processes (fig. 110. A, a) are very 

 long, and, being articulated by suture to 

 the bodies of the vertebrae, appear, at first 

 sight, like additional ilia. This is particularly 

 the case in a fossil specimen recently dis- 

 covered by Sir Charles Lyell.* The ilia (b) are 

 directed forwards and downwards, and the su- 

 perior extremity projects backwards in a trun- 

 cated point (<?)' The ischia (c) are larger, and 

 directed backwards at a great angle with the 

 ilia, uniting in a truncated median symphysis, 

 which is separated from that of the pubes ; 

 so that the obturator foramina are divided 

 only by ligament (g), and communicate in the 

 dry bones. In some Lizards the ischia present 

 posteriorly a spinous projection. The pubes 

 participate, with the ilia and ischia, in the for- 

 mation of the acetabula, present a spine at 

 their cotyloid extremity (d), curving down- 

 wards and outwards, and unite in a very 

 narrow symphysis ; but in the Monitors and 

 Sauve-gardes the pubic symphysis is distin- 

 guished by its greater breadth and truncated 

 form (/). The ilio-pubic angle is about 160, 

 retiring posteriorly in the Great Monitor 

 Lizard, and the ilio-ischial ansile is very acute, 

 being 60 only (see Jig. 112. fs.). 



In the Menepoma alleghani the sacral trans- 

 verse processes are directed backwards, and 

 support apophyses to which the ilia are at- 



* Lecture at the Royal Institution. 



tached. The pubes and ischia are short and 

 oblong, and so approximated as to leave no 

 obturator opening. 



Upon the pubic spine, in the Cameleon, are 

 two cartilages, which have been stated by 

 Duges to be of a marsupial character. 



A Fig. 110. 



A, jjelvis of the Great Monitor Lizard. 



B, ilium, ischio-pubis, and marsupial cartilage of the 

 Salamander (after Duges), seen from below, and 

 twice the natural size. 



From the pelvis of the fossil Pterodactyle 

 Cuvier concludes that the forward direction 

 of the ilia, the anterior position and pointed 

 extremity of the pubis, and the separation of 

 the pubic and ischiatic symphysis, ally this 

 animal to the Saurian reptiles. 



In the tailed Batradiia and Ichthycic rep- 

 tiles there is but one sacral vertebra supporting 

 rib-like transverse apophyses which connects 

 them to the ilia. The ilia are long and slender, 

 and the pubes and ischia are blended together 

 in one large, squarish, cartilaginous plate, not 

 perforated, and loosely connected by ligament 

 with the one of the opposite side. 



In the Proteus the ilia are small, and the 

 whole pelvis very little ossified. In the 

 Salamander, also, the ilia are small (see fig. 1 10. 

 B, a). A cartilage, of a Y shape (d], is placed at 

 the anterior margin of the ischio-pubic plate 

 (6), which Duges looked upon as marsupial, 

 but which Meckel has considered as part of the 

 sternal elements, and which is a bifurcated pro- 

 longation of the cartilaginous ischio-pubic sym- 

 physis (c). There is also a very small obtu- 

 rator opening in the ischio-pubic plate (). 

 The ossification of the pelvic bones in these 

 animals, according to Duges, takes place in the 

 same order as in man. The pelvis of theAxolotl 

 is, like that of the Salamander, not quite ossi- 

 fied. In the Siren, according to Cuvier, there 

 is no vestige of a pelvis. In the Ophisaurus, 

 C(Scili(E, and Amphisbcena, there are only rudi- 

 mentary vestiges of the ilia and ischia ; and in 

 the apodal Saurians, as in the Ojihidia, a single 

 bone only is found, under the skin near the 

 anus. In Pseudopus anguis and Acontia are 

 simple elongated pelvic bones, articulated by 

 ligament to the last dorsal transverse processes. 

 In Eryx boa a pair of elongated bones lie 

 parallel to the rectum, free from the spinal 

 column. They are sometimes found in several 

 distinct pieces. 



In the Sauroid reptiles the acetabula are di- 

 rected horizontally outwards, and the inflex- 

 ions of the feet are made perpendicularly to 

 the rachis or plane of motion, the thigh being 



