NO. 1666. OSTEOLOGY OF CAMPTOSAURUS—aiLMORE. 263 



Measurctncnts of specimen, Cat. No. 5818, U.S.N.M. 



mm. 



Greatest transverse diameter 139 



Greatest autero-posterior diameter 95 



The cdlcaneum. — Seen from the outside, the calcaneiim is subcres- 

 centic in outline. The upper surface is divided by a diagonal ridge 

 into two articular faces. The anterior one, which is above the heavier 

 enel of the bone, receives the distal end of the fibula. The posterior 

 articular portion has its surface below the level of the fibular surface 

 and is deeply concave antero-posteriorly, and receives the outer part 

 of the tibial malleolus. This portion has the greatest transverse 

 diameter. The posterior margin is rounded transversely and turns 

 up as a thickened roiuided lip. The ventral surface is convex from 

 front to back, the inner border being in contact with the outer edge 

 of the astragulus. The outer surface vertically is gently concave. 

 The calcaneum is represented in two individuals in the National 

 Museum, Cat. Nos. 5473 and 5961, also in the holotype of C. d'lspar., 

 No. 1877, Yale Museum, which, being the most complete element, 

 furnished the following measurements : 



Measurements of Specimen, No. 1877, Yale Museum. 



mm. 



Greatest extent autero-posteriorly of calcaneum 87 



Greatest extent transversely of calcaneum 55 



Distal tarsals. — The distal row of tarsals (see t, fig. 35) in Camp- 

 tosaurus consists of two flattened, cushion-like bones, which remain 

 distinct, never fused with the metatarsals, as Hulke has suggested 

 in I g^ianodon.^ and whose separateness would be restricted to the 

 embryo. The external one, viewed from above^ is subtriangular in 

 outline. Its proximal surface is shallowly cupped, the narrowed 

 portion being directed backward. The distal articulating surface 

 is concave antero-posteriorly and fits closely to the proximal end of 

 Metatarsal IV, as shown in fig. 35. There are deep longitudinal pit- 

 like depressions on the anterior and internal surfaces. Both proxi- 

 mal and distal articulating surfaces are smooth. The tarsal borne 

 by Metatarsal III is an irregular elliptical shaped bone, somewhat 

 thinner than the outer. Its distal articulating surface and all of the 

 surrounding edges are roughened and pitted. This surface is 

 slightly convex, while the proximal surface is gently concave and 

 quite smooth except near the edges. In specimen. Cat. No. 4277, 

 U.S.N.M., these elements have been retained by the matrix in their 

 mutual relationship with the metatarsals, so there can be no question 

 concerning their exact position. Even without this positive evidence, 

 the conformation of their surfaces with the proximal ends of the 

 metatarsals would have enabled one to place them accurately. 



