But while it is not now necessary to follow an assignment of error with a separate proposition, still, in the absence of fundamental error, the assignment, not otherwise appearing, must be brought forward from the back of the brief and presented as a proposition of law of itself and followed by such argument or discussion as is desired, with a reference to the authorities relied on and a clear accurate statement of the record bearing upon the assignment as required by rule 31. Western Casualty Co. v. Lapco (Tex.Civ.App.) 108 S.W.2d 740 (writ dismissed), opinion by Justice Brown, and decisions referred to, which is in accord with the opinion of the Commission of Appeals in Lamar-Delta County Levee Imp. Dist. No. 2 v. Dunn, 61 S.W.2d 816. Numerous decisions might be cited holding that failure of the complainant to comply with such requirements is fatal to the proposition urged either as an assignment of error of itself, or as a proposition in aid of an assignment; such as Terry v. Williamson (Tex.Civ.App.) 251 S.W. 813; Chicago, R. I. G. Ry. Co. v. Vesera (Tex.Civ.App.) 237 S.W. 349; Lancaster v. Crosby (Tex.Civ.App.) 263 S.W. 646; Brigman v. Holt Bowers (Tex.Civ.App.) 32 S.W.2d 220 (writ refused). Aside from the question of sufficiency of the assignments to present the issues of waiver and estoppel for the reasons embodied in the two propositions and statements thereunder (a question we will not undertake to determine and do not determine, in view of conclusions hereafter shown), it cannot be said that the court erred in refusing to hold that defendants' right to urge the defense of usury was waived, or that they were estopped to urged it by reason of their claim of title burdened with the provisions of the trust deed executed to Martin Stiles, trustee.