166 Annals of the Carnegie Museum. 



Extreme thickness of bone at the middle of the shaft 8 



Depth of notch at end of bone 15 



Length of linear median groove on convex surface no 



Length of groove on concave surface 65 



II. Bone found associated with the skeleton of Clidastes tortor Cope. 



This specimen shows at one end a deep notch somewhat similar to 

 the one observed in the specimen found with the skeleton of Mosa- 

 saarns lemonnieri. Only one of the projections forming the sides of 

 the notch (the upper one as represented in Fig. 5) is complete ; the 



Fig. 5. Bone belonging to Clidastes tortor Cope. % nat. size. 



other has been mutilated. The bone is thin. Both longitudinally 

 and laterally one surface is concave and the other is convex. A trace 

 of the rib-like longitudinal thickening of the middle of the shaft, so 

 well marked in the bone of M. lemonnieri, appears. The striae at the 

 bifurcated end are very distinct. The median grooves appearing on 

 both sides of the bone terminating in the notch in M. lemonnieri are 

 not found in this specimen. In spite of differences and imperfections 

 the close resemblance in form and structure to the better preserved 

 specimen from Belgium is manifest at a glance. 



Dimensions. 



mm. 



Extreme length of specimen 120 



Extreme breadth at the notched end 20 



Least breadth of shaft back of notched end 10 



Thickness of bone along edges 1-2 



Extreme thickness of bone at the middle of the shaft 5 



Depth of notch at the end of the bone.. II 



The function of these singular bones in the skeleton must remain 

 more or less problematical until future discoveries shall clear up the 

 question. The suggestion that they are interclavicles does not appear 

 to the writer at the present time as satisfactory. It is very hard to 

 conceive how such bones should have functioned as interclavicles. 



