104 



CRUSTACEA MALACOSTRACA. 



The genus is obviously different from all other hitherto known Mysidacea in having the last 

 thoracic segment (at least in the female) very elongated; dorsally it is not much shorter than the two 

 first abdominal segments taken together whilst ven trail y it is even considerably longer than dorsally; 

 the seventh pair of thoracic legs are inserted at its front margin. The carapace is tolerably short, 

 deeply incised posteriorly, so that the central portion of the penultimate thoracic segment is uncovered; 

 its lateral wings reach a little beyond the front margin of the last segment. The left mandible (fig. i f) 

 has the pars incisiva well developed, its lacinia mobilis has a large and strong cuspis incised at the 

 end, whilst behind this there is only a pair of weaker setae; the pars molaris is slightly marked, small 

 and weakly developed ; the whole margin from the base of the crtspis to the posterior end of the pars 

 molaris is furnished with fine hairs. The lobe of the second joint of the maxillse (fig. i h) is rounded, 

 with no protuberance, that on the third joint is cleft, the last joint of the palp unusually long, and 

 the greater part of the under side of this joint and of the lobes are densely covered with hairs. The 

 second joint of the maxillipeds (fig. i i) is long with a small but distinct lobe, the third very short 

 with a similar lobe, the 4 following joints with inconsiderable difference in length but decreasing out- 

 wards in breadth, so that the two last are fairly narrow. The first thoracic leg (fig. i k) has the 

 second joint in the form of a large plate as broad as long; the rest of the leg is slender, the sixth 

 joint somewhat shorter than the fifth, the claw well-developed. The other thoracic legs, which increase 

 somewhat in length from before backwards, are very slender (fig. i m) except as regards the second 

 joint, which is a large and broad plate; the sixth joint is considerably longer than the fifth without 

 obliqxie articulation, but its shorter distal part is separated as a distinct joint by a well-developed, 

 vertical articulation; the seventh joint and the claw are well-developed. The exopodite on the thoracic 

 legs (fig. 1 1) has the subbasal joint large and unusually broad, plate-like (the exopod of the maxilli- 

 peds was broken off). Antennae and tail-fan almost as in Meterythrops. 



It will be seen from these characteristics, that the genus must be placed in the Erythrops- 

 group, showing in a number of characters considerable agreement with Meterythrops, but there are 

 differences more or less in all the appendages described above in detail. 



Description of the Species. As there is only the mentioned incompletely developed speci- 

 men to hand, only the carapace, eyes, antennal scale and caudal process will be described here, the 

 other characters can be learnt from the description of the genus and the figures. 



The front end of the carapace, seen from above (fig. i c), is triangular, with median angle a 

 little over 90, but the very tip is produced in a very small process which is somewhat smaller than 

 the process on the eye-stalks. The eyes are yellowish and moderately small; seen from the side 

 (fig. i b) they look downwards a little and occupy the end of the eye-stalks in a flattened arch; seen 

 from above (fig. i c) they appear as a narrow band at the end of the stalk and are no broader than 

 this; above and close behind the eye at its centre the stalk has a protruding, distally rounded process 

 which projects forward over the eye. The squama (fig. i d) is moderately small, three times as long 

 as broad; its smooth outer margin is but little more than twice as long as the breadth, whilst the 

 setigerous terminal margin is very oblique and the distal outer corner has a short tooth. The outer 

 ramus of the uropoda (fig. i n) is defective, but nevertheless much longer than the inner branch, and 

 to judge from the serrulation the margins have undoubtedly been covered with setae over along 



