semi-cylindrical

According to the Merriam-Webster online dictionary, a bubble is a small globule typically hollow and light, a small body of gas within a liquid; a thin film of liquid inflated with air or gas; a globule in a transparent solid; something (as a plastic or inflatable structure) that is hemispherical or semi-cylindrical.

The Coming Death Bubble 2009

The side plumes are shorter, but are of a rich red colour, terminating in delicate white points, and the middle tail-feathers are represented by two long rigid glossy ribands, which are black, thin, and semi-cylindrical, and droop gracefully in a spiral curve.

The Malay Archipelago 2004

The grave was located in a small forest, the only grave in the area, and consisted of a large mound of earth heaped in a rectangular, semi-cylindrical shape over the remains, as is customary in CAMBODIA.

DEPARTMENT OF DEFENSE INTELLIGENCE REPORT 1996

The revolution of the discs carries the yarn through the dye-liquor contained in the lower semi-cylindrical part of the machine previously alluded to. (p. 049)

The Dyeing of Woollen Fabrics Franklin Beech

This new heating apparatus consists of a cast iron box, E, provided with an inclined cover, F, into which are fixed 100 copper tubes that are arranged in several lines, and form a semi-cylindrical heating surface.

Scientific American Supplement, No. 417, December 29, 1883 Various

The leaves are of a dull green, but not quite so dark as those of the Pinaster; they are semi-cylindrical, 6 inches or 7 inches long and one-twelfth of an inch broad, two in a sheath, and disposed in such a manner as to form a triple spiral round the branches.

Scientific American Supplement, No. 488, May 9, 1885 Various

The gas was generated in the lower part of the craft's semi-cylindrical metal body.

The Boy Inventors' Radio Telephone Richard Bonner

In any make the jig wince or wince dye beck consists of a large rectangular, or in some cases (p. 054) semi-cylindrical, dye-vat.

The Dyeing of Woollen Fabrics Franklin Beech

In many places the road was in that condition called _repaired_, having just been whittled into the required semi-cylindrical form with the shovel and scraper, with all the softest inequalities in the middle, like a hog's back with the bristles up, and Jehu was expected to keep astride of the spine.

The Atlantic Monthly, Volume 02, No. 08, June 1858 Various

A transverse cut is then made and the semi-cylindrical section thus severed from the log is removed.

Scientific American Supplement, No. 360, November 25, 1882 Various