320 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



riorly. The basal segment of the antennulse is enlarged; the second is 

 more slender and cylindrical ; the third is short, cylindrical, or slightly 

 clavate, and is followed by a short snbglobose segment having the ap- 

 pearance of a fourth peduncular segment. Beyond this, is a slender 

 multiarticulate flagellum, composed of about twenty to thirty segments, 

 the segmentation becoming indistinct toward the base. These segments 

 are provided, except toward the base, with slender "olfactory setae." 

 The first three segments of the antennae are short and robust, and the 

 second bears, near its distal end, on the external side above, a triangular 

 scale, or spine, articulated with the segment and directed forward, out- 

 ward, and somewhat upward ; the third segment is comparatively short 

 and small ; the fourth and fifth segments are slender and elongated, and 

 the flagellum tapers from the base and is composed of many, 80 to 120 or 

 more, segments. The maxillipeds (see pi. Ill, fig. 12 a) are broad, with a 

 rhombic-ovate external lamella (Z), and a five-jointed palpus (p), of which 

 the first three segments are flattened and expanded internally, where the 

 second and third segments are also ciliated. The last two segments of 

 the palpus are cylindrical, and bent inward toward the median line. The 

 outer maxillae are rhombic in outline, ciliated and spiny along the inner 

 margin and at the tip, as are also the two slender, curved, articulated 

 lobes. The inner maxillae consist of the usual curved lobes, armed at 

 the tip with denticulated spines, which are larger, stronger, and more 

 numerous on the outer large lobe. The mandibles are strong, and fur- 

 nished with an acute dentigerous lamella on the right side, received 

 between two such lamellae on the left mandible ; below is a comb of setae 

 and a strong molar process. The palpus of the mandible is composed of 

 three subequal segments, the last furnished with a comb of setae. 



The thoracic segments do not greatly exceed the head in transverse 

 diameter, and are subequal, the second, third, and fourth with a lateral 

 emargination. The legs are slender and elongated, ambulatory, or the 

 first pair subprehensile and somewhat shorter than the following pairs. 

 In this pair the carpus is slightly swollen and the propodus is capable 

 of complete flexion upon it. The dactyli are short in all the legs, as 

 compared with the propodi, and capable of only incomplete flexion. 

 They are armed at the tip with two robust unguiform spines. 



The pleon is broad and flattened above. The uropods are well de- 

 veloped and consist of a cylindrical or slightly clavate basal segment 

 bearing two rami of which the inner is the larger and longer. The un- 

 der surface of the pleon is excavated, and in the females is protected be- 

 neath by a subcircular operculum, but in the males of J. alta, and proba- 

 bly in both species, the thickened opercular plates are three in number, 

 viz, a pair of semi -oval plates at the sides and a more slender median 

 plate presenting traces of a suture along the middle. 



In the females, the incubatory pouch is formed of four pairs of plates 

 attached to the coxal segments of the first four pairs of legs. These 

 plates may usually be easily seen when the females are destitute of eggs, 



