Carte de Visite, Studio R.Wilkinson in Trowbridge.
Royal Wiltshire Yeomanry Trooper.

This trooper is displaying the silhouette as set out in 1858 - as described by Henry Graham in "The Annals ot the Yeomanry Cavalry of Wiltshire" (D.Marples & Co., Liverpool, 1886) :
"In 1858, some further alterations were made in the uniform. The red stripes on the overalls were altered to white, as were also the red facings on the tunic. The size of the shako was much reduced, and an upright "shaving brush " red plume substituted for the white horse-hair one."

It is interesting to see a carbine displayed here.
Westley-Richards "Monkey Tail" carbines were introduced in 1870 (ibid.) :
"Lord Ailesbury had a foot parade on the following Monday, and addressed the Regiment (...) He said that Westley Richard carbines would shortly be issued, though for his part he did not see that they were wanted, as they had already a number of men armed with rifles (...)".

Our trooper seems to be wearing Field Day Order Dress - as described in the "Rules and Regulations of the Royal Wiltshire Yeomanry Cavalry. Approved hy the Right Hon. Qathorne Hardy, Secretary of State for War, April 12, 1877." (ibid.) :
"Field Day Order.
To be used generally for Summer Drills, Divisional and Brigade field days, Garrison orderlies, mounted police in Garrison and Camp, and when specially ordered.
(...)

The cloak, when worn on the saddle, will be rolled 40 inches in length."

The shako would eventually be replaced in 1880 (ibid.) :
"In August, this year, the sanction of the Commander-in-Chief was obtained to the change of the shakoes to busbies"