Nebela triangulata  (Lang, 1865)
Basionym: Difflugia triangulata Lang, 1865

Original description. “I have lately met with an undescribed species of Difflugia; at least, I cannot find it either mentioned or figured in any published account of this genus. There can be no doubt that it is a distinct and peculiar species. The carapace, instead of being more or less spherical, globose, or pyriform, is almost flat and triangular, one of its apices being truncated to form an orifice for the emission of the pseudopodia. It is so remarkably transparent that the animal is seen, as through a glass case, suspended in the interior, and its surface is covered with markings of almost mathematical regularity.
I at first considered that this carapace was constructed of very minute pieces of pure diaphanous silica cemented together; but as, on drying it and subjecting it to the flame of a spirit lamp, it becomes more or less distorted, and the markings arc almost obliterated, I have come to the conclusion that it is more likely of a membranous nature. When the animal, moving through the water, presents the edge of its shell to the spectator, this is seen to have barely any depth, and looks like a cocked hat turned edgeways. I have found it in tolerable abundance associated with Difllugia spiralis, D. proteiformis, etc.; but as it is much smaller and extremely diaphanous, it may be easily overlooked.
The accompanying drawings of two separate specimens found in the same drop of water, although not artistic, are faithful representations of the creature and its house, having been carefully made under the microscope with the aid of the camera lucida.
If this is a new species, I think it may be appropriately named “triangulata.” — Fred. II. Lang, Reading.