Your text appears to involve opposition (i.e., administrative) proceedings at the Community Trade Mark Office, rather than civil proceedings in court, and the terminology used there differs from what would be usual in civil (judicial) proceedings. In that regard I believe you will see that "allegations", "pleadings", "submissions" and other terminology of civil procedure are not used in Community Trade Mark opposition proceedings. In the "Guidelines concerning proceedings before the Office for Harmonization in the Internal Market (Trade Marks and Designs)" on the Community Trade Mark Office webpage, "alegaciones contra la oposición" are simply called "observations (by the applicant) in response to the opposition" (and the verb is "to file observations against the opposition"):

2.1. Observations by the applicant in response to the opposition

IR 20(1)

Observations in response coming directly from the applicant or his representative must reach the Office within the specified period of three months or, if the `cooling-off' period is extended, within one month after the commencement of the proceedings.

IR 20(2)

In cases in which the Office has specified a time limit for the opposing party to give facts, evidence and arguments in support of its opposition, the response period runs from the date of receipt by the applicant of this information supplementing the opposition [15].

IR 20(3)

If the applicant does not file any observations within the period specified, the Office may rule directly on the opposition on the basis of the evidence received.

Lastly, observations from the applicant that reach the Office after the end of the three-month period, although communicated to the opposing party, are not taken into account by the Office.

http://www.uami.eu.int/en/mark/marque/directives/partiec.htm...

If you need additional vocabulary for your translation, here are links to the Community Trade Mark Office in both English and Spanish:

http://oami.europa.eu/en/default.htm

http://oami.europa.eu/es/default.htm







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Note added at 4 hrs (2007-10-22 15:45:58 GMT)
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For "ampliación de alegaciones" I would suggest "Additional Observations"