1956] 
Christiansen — Mesentotoma 
15 
up, and these may serve to fill out some of the blank spots 
in the phylogeny of the group. 
Genus Mesentotoma Salmon 
Mesentotoma Salmon, 1942. Records of Dominion Museum, 
1: 58,59. 
Body form oval to elliptical, circular in cross section. 
Antennae. Lengths of segments variable, commonly 1-2. 
5-2. 5-3. Second segment with a more or less definite 
indication of basal subsegmentation. Apical bulb of fourth 
antennal segment present or lacking. Head oval, only 
slightly longer than broad. Labral papillae lacking setae. 
Labial appendage with a well developed differentiated 
external seta. Legs with all setae eiliate except for normal 
apical internal smooth setae on third pair of legs. Tenent 
hair clavate or acuminate. Empodial appendage quadrilam- 
melate, widened for basal one-half to one-third of length 
and sharply acuminate for apical remainder. Internal 
distal edge often excavate. Unguis with from two to 
four internal teeth. The basal pair enlarged, often basally 
joined. Internal teeth large, basal in position and usually 
heavily reinforced. External teeth small or wanting. 
Mucro lacking basal spine, with small anteapical and large 
apical teeth. 
Mesentotoma exalga Salmon 
Figs. 8-10 
Mesentotoma exalga Salmon, 1942. Records of Dominion 
Museum, 1 : 58,59. 
Color and pattern. Background color yellow, pigment 
blue as follows: all of antennal segments two, three, and 
four; basal and apical rings on antennal segment one, 
plus ventral surface of this segment; ring around each 
antennal base and a connecting band. Small irregular 
spots over surface of head and a V-shaped mark in mid- 
region. Thoracic segment three through abdominal seg- 
ment three largely blue except for scattered small pale 
spots and pale regions along the posterior edges of dorsum 
of abdominal segments one and two. Anterior and posterior 
margins of abdominal segment four with large oval dark 
areas. Anterior margin of fifth and all of sixth segment 
dark. Distal part of legs slightly darkened, remainder 
