Based on the date of collection, I believe your identification is correct. But the specimens shown are very immature. Mature T. gibbosum is now known from late December thru early July. It tends to become much darker later in the year, and spores are more easily seen. The gleba (interior) also becomes a much darker color as it approaches maturity. When near the peak of maturity, it can be nearly chocolate-brown to nearly black interior, and the exterior will also have a distinctive darker coloration.
Daniel B. Wheeler