285 
1916-17.] Experiments and Observations on Crustacea. 
medial calcareous bar or keel, which, commencing between the two articular 
foramina for the maxillipeds, runs forwards towards the mouth, widening 
as it goes — see fig. 18. Ventrally the keel projects as a ridge (the dorsal 
aspect is correspondingly grooved like a gutter), with transverse indenta- 
tions corresponding to the joins between successive sternites; the articu- 
lations at these joins are rigid, not movable as in Bathynomus — see Milne 
Fig. 18. — Ventral aspect of “ cephalosome ” of Glyptonotus. 2^. Somewhat schematised. 
The calcified parts of the maxillo-sternal framework (with the exception of the borders 
of the paragnaths) are rendered in a lighter shade than the membranous parts. 
a, labrum ; b, lateral border of mouth ; c, ventral eye ; d, paragnath, with sickle- 
shaped calcification extending round lateral and ventral border ; e, styloid process ; 
/, transverse alar bar (the reference line is carried to a point which marks the lateral 
limit of attachment of the alar plate) ; g, anterior bar of first thoracic sternite ; h, 
keel of maxillo-sternal framework ; i, posterior bar of first thoracic sternite ; k, socket 
for anterior pivot of mandible ; l, mouth ; m, articular foramen for mandible ; n, 
articular foramen for first maxilla ; o, articular foramen for second maxilla ; p, 
articular foramen for maxilliped. 
Edwards and Bouvier (1902). Anteriorly the keel sends out two lateral, 
sickle-shaped, calcareous branches, which form the skeletal framework of 
the paragnaths. It ends just behind the posterior border of the mouth, 
being connected to the anterior heavy skeleton of the head by means of 
two broad bands of soft tissue, the lateral borders of the mouth. 
Laterally attached on either side of the posterior part of the keel are 
