NECTURUS MACULATUS. 431 
Bombinator). This gives a suggestion of homology between the later amphibian sternum 
and the sternebrum of the fourth myocomma alone, the shape and extent of which fre- 
quently remind one of the well known rhomboid plate of such a form as Salamandra. 
The procoracoid extends anteriorly as far as the first myocomma and its free anterior 
end is frequently covered by the transverse fold formed by the posterior border of the 
intermandibular muscle (M. intermaxillaris of authors) . 
Pelvic Girdle. 
The pelvic girdle consists of a flat ventral plate, the pubo-ischium, and two lateral 
pieces, the ilia, attached to the sacral vertebra by means of a pair of ribs. The ventral 
plate has an elongated pentagonal outline similar to that shown by the skull but with its 
longitudinal axis still more prolonged. The anterior median angle is especially tapering 
and extends along the mid-ventral line of the abdomen but shows no trace of an epipubic 
cartilage (cartilago ypsiloides) as in so many Urodeles. The ilia are attached along the 
posterior lateral sides and at their bases are situated the acetabula for the reception of the 
heads of the femora. As in the case of the skull, the posterior margin is slightly incurved 
and its outer angles (corresponding in position to the mastoid processes of the opisthotics) 
are somewhat prolonged and tuberculate, forming the tuberosities of the ischia. At about 
the middle of the pubo-ischium are seen two small obturator foramina which may be used 
as indicative of the boundary between the pubic and ischiadic elements which are here 
otherwise unmarked. A pair of osseous areas situated in the posterior half, and which 
develop and increase in size during growth, plainly represent the osseous ischia. The 
growth of these is well marked by concentric lines. The middle portion of the ilum is 
also ossified, the bone being a little curved and with a rounded dorsal, and a broad and flat 
ventral end. 
The ventral face of the pubo-ischium shows a slight muscular ridge along the middle 
line, and the dorsal or inner face is considerably excavated to form a pubo-ischiadic fossa 
for the accommodation of some of the viscera. The floor of the acetabulum is usually 
broken through by an acetabular foramen which leads into this last mentioned fossa. 
The lateral view (pl. 65, fig. 13) shows the manner in which the ilium is attached to 
the sacral rib. Instead of meeting end to end and forming a definite joint, the cartilag- 
inous ends of the two are prolonged and tapering and are applied to the sides of one 
another and held in place by firm connective tissue. The relations of this attachment to 
the vertebrae have been considered above under the vertebral column. In two cases 
which I have seen, a second ligamentous attachment appeared upon one side, extending 
