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This species is readily recognised by the shape of the genital segment and furcal joints, 
and also by the comparatively slender form of the fifth pair of feet. 
Porcellidium brevicaudatum has only previously been recorded from Ceylon. 
29. Family THALESTRIDAE. 
Genus Phyllothalestris G. O. Sars, 1905. 
Professor G. O. Sars has separated Thalestris mysts from true Thalestris on account 
of the enormous development of the fifth pair of feet of the female, and has established it in 
a distinct genus. 
One species is known. It was represented in the plankton collected by the ‘Siboga’ in 
the Malay Archipelago. 
1. Phyllothalestris mysts (Claus). Plate LXI, figs. 1—5. 
Thalestris mysis Claus, 1863, p. 130, pl. XVIII, figs. 12—16. 
Thalestris mysis Brady, 1880, vol. II, p. 121, pl. LVIII, figs. 1—3. 
Thalestris mysis T. Scott, 1901 (a), p. 354. 
Lhalestris mysis Thompson & Scott, 1903, p. 272. 
Thalestris mysis Pearson, 1905, p. 13. 
Phyllothalestris mysis Sars, 1905, p- 116, pls. LXX & LXXI. 
Phyllothalestris mysis T. Scott, 1906(a), p. 314. 
Phyllothalestris mysis Norman & T. Scott, 1906, p. 168. 
Two females identical with the above species were obtained from the plankton collected 
at the surface at Station 142, when the ‘Siboga’ was at anchor at Laiwui. 
The illustration of the fifth pair of feet given on Plate LXII, fig. 5, is similar in shape 
to the figure given by Sars in ‘Crustacea of Norway’ Vol. V. The surface of the fifth pair of 
the ‘Siboga’ specimens is marked by numerous interrupted transverse lines as shewn by the 
figure. Length of ‘Siboga’ specimens 1,9 mm. 
The very large foliaceous fifth pair of feet is a conspicuous character and enables the 
species to be readily recognised. 
Phyllothalestris mysis appears to be rather widely distributed. It has been recorded 
from the British and Norwegian Coasts, from the Mediterranean, from the Gulf of Suez, and 
from the Island of Ceylon. 
Genus Rhynchothalestris G. O. Sars, 1905. 
The members of this genus can be distinguished by the unusually sharp division between 
the cephalothorax and the abdomen, and by the very large rostrum. 
Two species were represented in the material collected by the ‘Siboga’ in the Malay 
Archipelago. One of the species does not appear to have previously been described. 
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