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 aud extent of which fre- 

 quently remind one of the well known rhomboid plate of such a foi-m as Salamandra. 

 The procoi'acoid 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 Hat 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 jJentagonal 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 pi'ocesses of the opisthotics) 

 are somewhat prolonged and tuberculate, forming the tuberosities of the ischia. At about 

 the middle of the pul>o-ischium are seen two small obturator foramina which may be used 

 as indicative of the boundary between tlie 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 Unes. The middle portion of the ilium 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 wliich leads into this last mentioned fossa. 



The lateral \aew (pi. 6-3, 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 



