NO. 2127. 



OSTEOLOGY OF THE8CEL0SAURV8—GILM0RE. 



609 



Below the obturator process the ischium retains about the same 

 width to the slightly thickened distal extremity. The inner borders 

 of the lower third of the ischia were in contact as shown in the articu- 

 lated pelvis and also by the ischium of the American Museum speci- 

 men (Cat. No. 5031, A.M.N.H.) which exliibits a flattened, thick- 

 ened face for this union. The distal 

 ends of the ischia in the type were 

 largely missing and have been re- 

 stored, but their length and shape 

 could be quite accurately determined 

 from the impressions remaining in 

 the sandstone. 



Rils. — All of the known presacral 

 vertebrae bear ribs. The four ver- 

 tebrae immediately preceding the sa- 

 crum carry single-headed ribs, aU 

 others being double-headed. 



In the neck, as shown by specimen 

 No. 7758, the cervical ribs are short 

 with the usual forked vertebral end. 

 Their free end is rounded and pointed, 

 and is extended antero-posteriorly. 



The anterior thoracic ribs are con- 

 siderably curved near the upper ex- 

 tremities. The shafts are moder- 

 ately broad antero-posteriorly with 

 truncated lower ends. The tuber- 

 cular branch is reduced to a mere tu- 

 bercle placed on the superior border 

 where the long capitular branch joins 

 the shaft of the rib (fig. 18). The 

 distance between the capitulum and 

 tuberculum gradually shortens pro- 

 ceeding posteriorly, until on the 

 fourth in front of the sacrum both 

 blend in a single articular facet which 

 attaches to the end of the transverse 

 process. Whether these ribs become 

 ankylosed to the transverse process 

 at the end as they do in Hypsilopho- 

 don can not be surely determined, though it is likely in an aged indi- 

 vidual they would become firmly fastened. 



These single-headed ribs are directed decidedly forward. 



81022°— Proc.N.M.vol.49— 3 5 39 



Fig. 18.— Right thoracic bib of Thesce- 



LOSAURUS NEGLECTUS GH-MORE. T^iTE 



No. 7757, U.S.N.M. J NAT. SIZE. Viewed 

 FROM the front, c, Capitulum; t, tu- 

 berculum. 



