Towards the start of the 1870's the hoop skirt was soon replaced with a metal structure known as a bustle.
The bustle still kept fullness at the front but allowed more fabric and layers to create more fullness at the back of dresses. Most of the dresses were trained but walking dresses are still floor length.
Knee length overskirts were still popular. If you look at the image below knee length overskirts look like an apron/tunic.
At the start of the 1870's bodices ended at he natural waist and were often belted around the waist or tied with a large ribbon at the back. Towards the middle of the 1870's the bodices started moving their way down to the hips to a basque. A basque is a very small over skirt which soon became attached to the bodice.
Evening skirts were off the shoulder with lots of trims and ruffle detailing while day wear usually had a high neckline. If the day dress had a drooping neckline a Chemisette would be worn. A Chemisette is like a blouse that finishes at the waist and was work under many gowns in the Victorian era.
By 1873 Polonaises were worn. A Polonaise is a bodice and overskirt that is attached together as one. The skirts began to become narrower at the front and layers of the skirts would be trimmed separately to create a beautiful effect and fullness. Sleeves became narrower (yet not skin tight) and followers but intricate cuffs.
Bustles became smaller by 1875 and were soon left home completely.