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Androcyclas gamphonycha
(Jørgensen, 1900)
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Description - Add description
Androcyclas gamphonycha:
The region of the neck is very peculiar, not forming any distinct stricture between the cephalis and thorax, but a zone where these two joints gradually pass into each other. This region appears on the dorsal side to lie between two pair of branches from the apical spine, D, namely two dorsal, lateral spines below (corresponding to those in the genus Amphimelissa) and the primary, lateral arches above. These dorsal, lateral spines (from the base of the spine A and the spine D) lie near the hind wall of the cephalis. The lower part of the apical spine, D, is here a columella in the region of the neck, but lying near the cephalic wall.
The length of the abdomen varies considerably, probably according to age; this is also the case with the number of byspines. It is not unusual to find comparatively well developed forms which are apparently almost or entirely without the characteristic byspines, but which in other respects diverge so little from the typical forms that they can scarcely be considered to belong to any other species. Therefore I now think that Pterocorys theoconus must be looked upon as a form of this species.
The other, very short tophorn is very rarely seen distinctly and is probably a more or less accidental formation. Sometimes strong siliceous edgings are developed on the upper part of the cephalis, and these may be protruding and in certain positions look like a very broad, short spine.
According to my experience no limit either can be drawn between Pterocorys gamphonyxos and P. amblycephalis. The younger forms seem to answer best to the latter, which is in appearance so different to P. gamphonyxos that it is generally easy to keep them distinct. (This is done in the tables). The principal difference is that P. amblycephalis has a cephalis which is at the upper part abruptly cut off and, at the very top, often open. This opening is probably closed later on. The tophorn is generally shorter and more weakly developed and the abdomen short and broad, without distinct byspines, all characteristics which may be explained by supposing that P. amblycephalis is the younger stage of development. On individuals which it seemed more correct to refer to P. amblycephalis than to P. gamphonyxos, I have also occasionally seen short and broad byspines in conjunction with a better development of the abdomen.
On the best developed specimens of A. gamphonycha, the abdomen is again narrowed below, the strongest set of spines being on that part which is broadest. The byspines are only slightly bent.
Frequent, in Tranødybet 6/4-1899, 0-630 m., numerous, otherwise rather sparse and generally only in deep water.
Distribution: On the west coast of Norway, in deep water, rare. Off the coast of Finmark 5/3-1901, in a surface sample (S/S Michael Sars cfr. Gran, 1902, p. 154). Perhaps a temperate oceanic form.
| | Jørgensen 1905 |
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