GLYPHOCRANGON NOBILIS. 143 



dorsal keel, most pronounced near the anterior end, runs backwar'd, becom- 

 ing obsolete abreast of the posterior pair of lateral spines. In neaily all of 

 the specimens the dorsal side of the rostrum is roughened in the middle por- 

 tion of its length by transverse corrugations on each side of the median 

 carina. The lower face of the rostrum is distinctly margined ; the margins 

 gradually converging at each end, leaving between them a lanceolate field 

 which is divided anteriorly by a light median carina. This median ventral 

 carina of the rostrum is characteristic. I have found it wanting in but one 

 or two out of the twenty-three specimens examined. The general trend of 

 the rostrum is lightly downward to a point near the tip, then upward to 

 the tip. 



The two or three tubercles that represent the anterior part of the second 

 lateral carina of the carapace are produced to spinous points, the foremost 

 forming a pair of prominent spines at the front part of the gastric region. 

 The prominent carina (fourth) which runs along the hepatic area is produced 

 at its anterior end into a distinct, acute, though not large spine, which is 

 divided from the rest of tlie carina posteriorly by a notch or sinus. All the 

 carintB except the two uppermost have a worn and eroded surface. The an- 

 terior part of the third crest is represented by a single tubercle on the hepa- 

 tic area. The lower margin of the second abdominal pleura is often one- 

 toothed, the anterior and posterior angles being rounded off and destitute of 

 spines. The tubercles of the abdomen are more sparse and less pronounced 

 than in the type of G. nobilis, as inferred from Milne Edwards's figures. The 

 telson, like the rostrum, varies in length in different specimens. In those with 

 the longest rostrum the telson is one-third longer than the swimmerets, while 

 in others it is not over one fifth longer than these appendages. It is up- 

 turned at the tip, very lightly in the majority of specimens, but very 

 strongly so in the specimens with the longest telson. There is a later- 

 ally compressed tooth in the median dorsal line at the base of the telson 

 which forms the posterior end of the median carina of the abdomen. The 

 dorsal pair of longitudinal carina3 are obsoletely spinose on their anterior 

 third. 



In the type specimen of G. longirostris Smith, the rostrum is widened mid- 

 way between the anterior pair of lateral spines and the tip, thus assuming 

 a lanceolate outline ; the corrugation of the dorsal surface of the rostrum 

 is more emphatic than in the " Albatross " specimens, and the median dorsal 

 carina is continued backward to the gastric area ; the tubercles on the an- 



