Plate XXII., fig. 1: a, front view; b, suture; c, side view.
On the Identity of Amphicampa with Himantidium, and Description of a new Species.
[Read before the Philosophical Institute of Canterbury, 4th August, 1881.]
About four years ago I found, quite accidentally, in a drain in the Cust Valley swamp a small pocket of diatomaceous earth, which on examination much resembled Amphicampa mirabilis, Ehr., described in the Micrographical Dictionary as a doubtful genus of fossil Diatomaceæ. The other species named is A. eruca, and both are represented as found fossil at Tizar, Mexico.
Professor Hutton found fossil valves in Waikato and elsewhere, and Mr. George Gray recognized them in gatherings taken from the River Avon.
In the month of May last I gathered a considerable quantity of a filamentous Diatom from a spring at Ngapari, Fernside, which, after treating in various ways, I resolved into the hitherto so-called genus Amphicampa (both sides sinuated). That genus, however, appears to have been considered “free,” while in the form which I gathered it is filamentous, and cannot be separated generically from Himantidium. The resent species is, however, certainly not A. eruca; and as A. mirabilis is figured with 7/6 bends, while my species varies from 4/3 to 6/5, I assume it to be a new species.
Himantidium maskellii, sp. nov.
Frustule: front view rectangular; length about four times the breadth, straight, forming a lengthened tenacious filament, showing lines of dots at the points of suture corresponding to the striæ on the side view. Valve: elongated, slightly arcuated, and attenuated towards the extremities, which are boldly rounded; both edges are sinuated; length about seven times the breadth. The convex edge has invariably one more bend than the concave. The valves vary in the number of the bends from 4/3 to 6/5. Striæ: parallel and transverse, and there are 23 to 27 to the .001 of an inch.
Hab.—Ngapari, Fernside, and River Avon, North Canterbury; Waikato and Cabbage Tree Swamp, Auckland (fossil)-Hutton; Cust Valley Swamp, North Canterbury (fossil).