1916-17.] Experiments and Observations on Crustacea. 253 
the sternites. The articular foramen, considerably larger than the inserted 
articular extremity of the basipodite, has a border which therefore lies 
in the horizontal plane. Its outline may be compared with that of a 
Cupid’s heart — see fig. 2. The apex of the heart points on the whole 
Fig. 2 . — Glyptonotus antarcticus from the ventral aspect. Photograph. Natural size. The 
thoracic limbs on the left side of the animal have been disarticulated at the coxo-basal joint. 
Note (i) the flat ventral surface and the absence of ventrally hanging coxal plates ; (ii) 
the division of the thoracic limbs into two groups and the system of alternate flexures in 
each limb ; (iii) the presence of an articular spur in each coxal foramen (those in the anterior 
three foramina are not distinct in the photograph — c/., however, fig. 15. p. 280); (iv) the 
presence of a medial split in the majority of the thoracic sternites. 
medially ; the base is asymmetrically cleft by a medially pointing process, 
which will be referred to as the articular spur of the coxa. Owing to the 
direction of this spur, which does not point towards the apex but rather 
towards the anterior border of the Cupid’s heart, the anterior of the two 
hays into which the base is thus divided is deeper and has a wider sweep 
than the posterior. 
