Lasanius

Lasanius is a genus of basal anaspida from the Late Silurian. Its fossils are around 27 mm to 40 mm in length.
Fossils have been found in Late Silurian-aged strata in Ayrshire, Muirkirk, Scotland and Seggholm.
References.
R.H. Traquair M.D. LL.D. F.R.S. (1898) IX.—"Notes on Palœozoic fishes."—No. II, Annals and Magazine of Natural History, 2:7, 67-70, 
Traquair, R. (1899). XXXII.—Report on Fossil Fishes collected by the Geological Survey of Scotland in the Silurian Rocks of the South of Scotland. "Transactions of the Royal Society of Edinburgh," "39"(3), 827-864. 