Description - Add description
Length 0,065mm. Breadth 0,05mm. Cephalis trilobate, with rounded, irregular pores and some scattered setae. Thorax twice as long as the cephalis, with very irregular pores of different size.
This genus in outward appearance is similar to Lithomelissa, but its structure is principally different. It has the most important spines of the Campylacantha type, namely the four primary ones, A, D, Lr and Ll, one ventral, sagittal spine, and two strong lateral, dorsal ones, rising from the base of the spine D, which here, as in Lithomelissa, appears as a protruding, apical spine. The primary arches too are strongly developed, the ventral arch, namely, as well as the right and left lateral arches (cfr. Plectacantha) all as arches inside the cephalis. To these come a couple of strong arches from the dorsal, lateral spines to the primary, lateral arches, also situated inside the cephalis, near its sides.
These strong inner arches are all connected outwards with the lattice shell, by means of strong, supporting beams which, for the most part, protrude on the exterior, as fine, long spikes.
This peculiar form is only distantly related to the others in my material. In structure it is unmistakably similar to Phormacantha hystrix; but there are, nevertheless, as far as I have hitherto been able to see, important differences in the structural type. The distinctly enclosed columella (the spine D) is characteristic; it shows, from the dorsal side, two basal, obliquely downwards pointing side branches, the dorsal, lateral spines, and higher up two obliquely upwards pointing ones, the usual primary branches of the spine D. Probably the two strong arches from the dorsal, lateral spines to the right and left, primary, lateral arches correspond to the comparatively strong apical arches, which in Phormacantha hystrix extend from the primary branches of the apical spine A to the lateral arches. In this case, the dorsal, lateral spines might be considered to be, centrally displaced, primary branches of the spine A, and this answers to their direction.
The genus Amphimelissa then has an inner, incompletely latticed cephalis, surrounded by a lattice shell, which immediately continues downwards as a thorax.
The rather intricate course of these inner arches and skeleton parts here, as in the genera Lithomelissa and Acanthocorys, is difficult to trace in its details, as the outer lattice shell generally conceals them. So there are in this genus, as in the other two above mentioned, several structural details which require closer investigation. So much is, however, certain, that no satisfactory, natural system of classification for the Cyrtoidea group can be formed, unless the necessary consideration is paid to these inner skeleton parts.
The genus Amphimelissa ought undoubtedly to be kept distinct from the peculiar, irregular forms which form Haeckel`s division Botryodea.
The transverse section is a short oval, with the longitudinal axis in the direction of the central rod (sagittally). There are three large swellings on the upper part of the shell (the “cephalis”), a dorsal one, between the spines A and D, and two lateral ones on each side extending forwards to the ventral side.
I earlier confounded this species with Lithomelissa setosa and it is entered in the tables under this name. It seems however, on the whole, to be very rare. It is interesting that it seems to occur during the spring diatom inflow.
Malangen, 29/1-1899, 0-300 m; Lille Molla, 1/4-1899, in the surface.
Distribution: Rare on the west coast of Norway. Mentioned by Cleve from places in the northern and western Atlantic, as far as to the west of Spitzbergen, here at great depths (76°-78°N, 15°E-3°W, deep sea hauls from 325 m and more, Aug. and Sept. 1898; 71°-72°N, 21-22°W, hauls from 180 m and more, July 1899; 45°N, 49°W, high salinity and temperature, January 1899).