— Generic features. The structure of the thoracic limbs is are markedly more unguiculate than in any other genus of mysids. The claw is surrounded by a stiff brush of long, peculiar, microscopically spinose setae, giving a very characteristic appearance which can readily be recognised.
Carapace rather short. Antennal scale with outer margin naked and ending in a thorn, apex obliquely truncate. Eyes well developed.
Labrum much longer than broad, produced anteriorly into very long process.
Mandible molar tubercle feebly developed; maxillae narrow, lobe from the third segment feebly cleft.
Proximal segment of exopod of uropod armed with spines but no setae. Endopod of uropod undivided.
Thoracic endopod markedly unguiculate. First pair of thoracic limbs slender, gnathobasic lobe on the second segment only of the endopod or entirely absent; third pair of thoracic limbs with the endopod not elongated and dactylus and claw well developed; pleopods of female reduced to small, simple, linear plates with a few plumose setae. Exopod of uropod with distinct distal suture. Telson entire.
Three pairs of oostegites in the female.
— Species. General form very similar to that of S. clausii, but slightly more robustly built, especially in the region of the abdomen.
Exopod of uropod with a distinct distal suture. Antennal scale with outer margin naked and ending in a thorn. Telson entire. Thoracic endopods markedly unguiculate.
Carapace short leaving the two last thoracic segments exposed.
Antennal peduncle in the female with the inner margin of the third segment armed with three long, plumose setae in addition to the group of three of four at the base of the inner flagellum.
Antennal scale very similar to that of S. clausii, except that the other margin is very slightly concave.
Mandibles with molar tubercles feebly developed.
Eyes with cornea occupying about one-third of the whole eye.
Thoracic limbs markedly unguiculate. The claw is surrounded by a stiff brush of long, peculiar, microscopically spinose setae, giving a very characteristic appearance which can readily be recognised.
Telson very similar to that of S. clausii , but the spines arming the lateral margins appear more crowded. From 2 to 6 small spines in the intervals between the large spines.
Uropods much slenderer than in S. clausii, exopod with 10 to 15 spines on the outer margin.
Transparent sometimes a darkbrownish-black colour.
Adult up to 15 mm.
Siriella jaltensi is not quite so strictly littoral in its distribution as is S. clausii, having been taken in numbers as far as 1250-2000 m. from the shore.
Siriella jaltensi has much the same distribution as S. clausii and usually occurs with it.
Distribution in the North Sea
Western North Sea, maybe entering from the Channel, littoral.
Atlantic Ocean: <26 -58°N; Mediterranean; Black Sea; coastal.
[After Tattersall and Tattersall, 1951]