Lissodendoryx (Ectyodoryx) atlantica (Stephens, 1921) is a thinly encrusting deep water species recorded from 75 m off Roscoff. It is ill-known. Identification is only possible with microscopic examination.
Shape, size, surface and consistency: Thinly encrusting sheet of 3 cm in diameter, 1-3 mm in thickness. Slightly raised oscular papillae
Spicules: Megascleres: The ectosomal spicules are strongyles, with rather unequal ends, one end being slightly thicker than the other; the shaft is often a little crooked; size is 400-500 x 6 µm. Large acanthostyles have a slightly curved shaft; the head is swollen and is covered with short, blunt spines. A few spines are sometimes scattered along the shaft for a short distance; on the other hand, some of the spicules are almost quite smooth; these spicules measure about 660-950 x 15-21 µm. The echinating acanthostyles are small and few in number; the shaft is straight, the head is a little swollen and is covered with rather long spines; the shaft is thickly set with small, recurved spines; size is 100-140 x 10 µm.
Microscleres: Arcuate isochelae; the shaft is fairly strongly curved; it is about 10 µm in breadth in front view; the teeth are rather short; the chelae measure 45-60 µm.
Skeleton: The ectosomal spicules form thick bundles, arranged tangentially; there are large quantities of microscleres at the surface. The main skeleton consists of a network of large acanthostyles lying usually 3 or 4 together, sparingly echinated by small acanthostyles. A small quantity of spongin is present.
Ecology: Deep water, from 75 m downwards, on stones.
Distribution: W coast of Ireland, Roscoff.
Type specimen information: BMNH 1910.1.1.901 (dry). Co-type. Norman Collection + BMNH 1922.214.171.124 (slide).
This is a deep water species recorded from 75 m off Roscoff. It is ill-known. The subgenus Lissodendoryx (Ectyodoryx) may be distinguished from Hymedesmia and Phorbas by its reticulate skeleton.
Source: Stephens, 1920.