Body transparent. Two pairs of lateral fins, partially rayed and connected with a fin bridge. Anterior fin long and rounded, beginning near the posterior end of the ventral ganglion. Posterior fins are angular in shape. Collarette and alimentary diverticula absent. Eyes small, with small pigment spot. The number of hooks decreases with maturity. Hooks change in shape in older specimens into "secondary hooks".
Ovaries long and broad, reaching up about 2/3 of the length of the anterior fin. Seminal vesicles small, conical in shape, locate close to the posterior fins.
Hooks: 3-10; the number decreases with maturity. Teeth in two rows, anterior 2-8 and posterior 5-12.
Maximum body length 42 mm; relative tail length 15-17%.
Epi- to mesopelagic.
Distribution in the North Sea
S. lyra might occur in the northern North Sea.
Oceanic, in warm and temperate waters.
In identification, Sagitta lyra might be confused with Sagitta maxima. In Sagitta lyra the anterior fins begin at the posterior end of the ventral ganglion; in Sagitta maxima these fins begin at the middle of the ventral ganglion. The relative tail length in Sagitta lyra is smaller than in Sagitta maxima.
[After Pierrot-Bults and Chidgey, 1988]