96 Transactions of the Royal Society of South Africa. 
sternum serves as an attachment for the membrane which is connected to 
tlie first pair of abdominal hoops. 
Text-Fig. 12.— Sternal Arrange- Text-Fig. 13.— Sternal Arrange- 
ment IN C. brevicornis. ment in C. lateralis. 
Text-fig. 13 shows the sternum of C. lateralis ; it is chiefly pecuhar in 
the length and breadth posteriorly of the xiphoid process. 
The highest specialization appears to take place in the dilepis group, as 
exemplified in this paper by C. quilensis and G. dilepis. Normally (Text- 
Text-Fig. 14. — Typical Arrangement op 
Sternal Ribs in C. dileins. 
fig. 14) three pairs of ribs are attached to the sternum, but sometimes 
there are four. The xiphisternum is rather small. A membrane attaches 
