PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 495 



short, somewhat trniicated and miuiitely deutate process. The sec- 

 ond segment of the peduncle of the antenna is armed with a denti- 

 form process below and a sharp tooth on the outer side; the third 

 segment is armed with a single large distal spine on the outside ; the 

 fourth and fifth segments are only inconspicuously armed. The tia- 

 gellum is slightly compressed, more than twice as long as the cara- 

 pax, and sparsely clothed with slender setae. 



The infero-mesial edge of the merus of the second gnathopod is armed 

 with three conical spines. 



The chelipeds are not very much longer than the carapax, including 

 the rostrum, and very stout ; the merus is considerably shorter than 

 the chela and armed with a few sharp spines along the dorsal edge and 

 at the distal end, and with numerous small tubercles ; the carpus is 

 armed somewhat like the merus, but there are more and smaller spines 

 at the distal end; the chela is about as long as the breadth of the car- 

 apax between the hepatic spines, more than a third as broad as long, 

 considerably compressed vertically, somewhat roughened with small 

 tubercles, especially along the inner edge, and with the stout and 

 straight digits making more than half the whole length. The three 

 pairs of ambulatory peroeoi)ods are very nearly alike and a little longer 

 than the chelipeds ; the meri and carpi are roughened with small tu- 

 bercles, angulated, and armed with a series of spines above; the pro- 

 podi are angulated, with all the angles rough and tuberculous and the 

 dorsal spiny ; the dactyli are very stout, very slightly tapered except 

 near the curved, acute, and chitinous tip, and armed along the lower 

 edge with a series of stout spiniform teeth which rapidly decrease in 

 size and become obsolete proximally. The posterior peraeopods are 

 very nearly as in the allied species. 



The pleon is about as broad as the carapax, only slightly narrowed 

 posteriorly, and the dorsum is transversely rounded and devoid of lon- 

 gitudinal carinae, teeth, or spines. The second and third somites each 

 have two slightlj^ roughened transverse ridges upon the dorsum sepa- 

 rated by a smooth sulcus, but the dorsa of the succeeding somites are 

 nearly smooth. The posterior margin of the sixth somite projects in a 

 prominent median lobe, with a smaller and much less prominent lobe 

 either side. The exposed parts of all the pleura are sparsely tubercu- 

 lous and their lower edges obtuse. The second pleuron is broader than 

 the others and its anterior edge upturned, leaving a broad depression 

 between it and the prolongation of the transverse carina of the dorsum, 

 which makes a median ridge. 



The telson, uropods, and pleopods are very nearly as in M. Bairdii 

 and M. rostrata. 



The eggs in the recently preserved alcoholic specimen measure 3.4 by 

 3.6""™ in less and greater diameter. 



Measurements are given further on with those of the next species. 



