Description of (fenera unci Species. 45 



Movable rostrum with wide base becoming suddenly constricted and ending in a 

 keeled bayonet-shaped bent down point ; posterior margin deejily concave. Tail long 

 and tapering, with traces of median and lateral keels in the form of a backwardly- 

 directed spine which increases in length of base on each succeeding segment. Telson 

 narrow and shield-shaped, with prominent central keel and long hastate median spine. 

 Uropods as in P. stocki, but external brancli not so long proportionatelv. Members 

 differ slightly in proportions. 



General Description. — As will be seen at a glance from the figures given of this 

 species, it had the liabit of preparing for interment as already described, so that it almost 

 invariably gives a side presentment with the carapace and head organs bent over so as 

 to expose the tergites of the trunk segment. In fig. 4, where the carapace is tilted 

 rather further than usual, all the seven last trunk segments are seen. These decrease 

 in size from behind forwards. The carapace is usually shown doubled together, and is 

 seen to be a little more elongated and more deeply cut out at the back than in 

 the type species. A trace of the median keel is seen in some specimens (fig. o) in 

 front of the cervical fold, but there is no means of knowing whether it appeared 

 in the area behhid. The lateral and dorso-lateral keels are faintly indicated 

 in fig. 2. Figs. 2, 3, and 5 show the rostrum. In the case of fig. 3 it is bent relatively 

 to the long axis of the carapace, showing it to be moveable, and iii fig. 2 it is seen to be 

 actually oat of place. Two small knobs are often seen, one at each of the angles of the 

 base, and the rostrum is I)ent down towards the tip. The tail is constructed as in the type 

 species, but the last four segments show three rows of spines corresponding to the median 

 and lateral keels. A trace of the media!i one is shown in fig, 2 on the second tail segment 

 as a protuberance near the posterior margin. It is more pronounced on the succeeding 

 segment, becoming a veritable keel on the fifth or sixth segments. The lateral keel 

 spines do not reach so far l^ack as the median ones. The segments are all supplied 

 with the usual large epimeral lappets, which are directed downwards and are almost 

 square, witii rounded angles in front and pointed behind. Tlie lappets are each bounded 

 on their anterior and inferior margins by a thickened band, terminating in a 

 spine, the spine ending in front of the posterior angle and nearer to it in each succeed- 

 ing segment. The epimera overlap each other from before backwards, and ei-en 

 when the tail is extended to tlie full are not (juite free from (»ach other, thus 

 adding greatly to the strength of the tail and forming a complete protection to the 

 pleopods. So much so is this the case tliat the pleopods are .seldom visible. The 

 telson is amitely heart-shaped, or rather shield-shaped, and narrow compared with 

 other species, and ends in a spear-shaped spine which is in direct continuation 



