66 J. B. Johnston. 
ABBREVIATIONS USED IN ALL THE FIGURES. 
arch., archenteron. 
ch.op., chiasma opticum. 
c.s., corpus striatum. 
d., dental ridge. 
d.max., portion of dental ridge forming maxillary teeth. 
d.vom., portion of dental ridge forming vomerine teeth. 
en., entoderm. 
ep., epiphysis. 
h., hyoid arch. 
hy., hypophysis. 
m., mouth plate. 
mand., mandibular arch. 
max., upper jaw. 
n., neural plate or neural tube. 
nch., notochord. 
o.ph., oro-pharyngeal cavity. 
p., preoral or palseostomal recess in the archenteron. 
pr.en., preoral entoderm. 
prm., premandibular somite. 
r.m., recessus mammillaris. 
r.p., recessus preeopticus. 
r.po., recessus postopticus. 
t., terminal ridge or chiasma ridge. 
t.b., taste bud. 
y.tr., velum transversum. 
