delivered the opinion of the Court:

The settled limitation upon the amendment of applications in respect of claims is that there must be a basis for them in the *460description and specifications of the application as originally filed. Re Dilg, 25 App. D. C. 9, 19. The burden is upon the* appellants, therefore, to show that this claim 36, which is the only one now in issue, was within the description aforesaid. There was a difference between the decision of the Examiners-in-Chief and the Commissioner as regards the latch mechanism in the mold-board section. He sustained their decision denying the claim, however, maldng the following statement:

“I am not convinced, however, that the latch may be considered as being ‘mounted upon one mold-blade section,’ as stated in this claim. The latch or cross-pin is described by applicants as — ‘* * * movable in its bearings and caused to act upon the upper section 10, to advance and retract it as-desired. In the present embodiment the cross-pin 12 is longitudinally movable and is formed in cross-section with a straight-section 13 riding in a slot 14 in the lower mold-blade section 11.’

“It seems clear from the applicants’ disclosure that the bearings for the latch are formed in the arms of the slide 2, and the straight section 13 of the latch merely rides in the slot in the' mold blade. Manifestly, the latch is ‘mounted upon’ the slide,, and not on the mold blade, as required by this claim.”

The ambiguity in the description in the application as applied to this particular mechanism is apparently due to the'fact that this claim was not in mind when the application was prepared, and has been suggested by the claim of a conflicting application. Without going into the question at length, we think it sufficient to say that we are satisfied with the statement which has been quoted above from the Commissioner’s decision. The expression “mounted upon” seems to have an ordinary meaning in machine construction. The thing mounted upon another must be borne or supported by it. Mere riding in or over another in a slot for the purpose, although operating in connection therewith, is not equivalent to being mounted thereon.

• Finding no error in the decision rejecting claim 36, it will *461be affirmed. ■' It is ordered that the clerk certify this decision to the Commissioner of Patents, as required by law.

Affirmed.