310 COPE. 
EXPLANATION OF PLATE XXIV. 
Fic. 1. Rana virescens, adult, X 2; @, squamosal bone; 4, ear bones without 
epistapedial. 
Fic. 2. Rana virescens, larva with hind legs, and developed fore legs concealed, 
the skull X 2; a, the hyoid apparatus from below, X 4. 
Fic. 3. Rana catesbeyana, larva further advanced than that represented in Fig. 2; 
showing the first appearance of the auditory cartilages at ST and AT. 
Fic. 4. Zrimerorhachis insignis of the Permian bed of Texas; part of skull from 
below, showing columella at s¢.; natural size. 
Fic. 5. Zvrimerorhachis insignis basicranial axis from below, without stapes; 
natural size. 
Fic. 6. Zatrachys serratus, wpper posterior part of skull from above; natural 
size. 
Fic. 7. Zatrachys serratus, inferior view of external part of posterior part of 
skull of individual represented in Fig. 6; showing columella. 
EXPLANATION OF LETTERING. 
A.T., Annulus tympanicus; B.0., basioccipital; C.Br., Ceratobranchial; C.Z., 
Ceratohyal; C.77.,Cornutrabeculi; £.5., Epistapedial; £7z., Ethmoid; 4£x.0., Ex- 
occipital; #.P., Frontoparietal; A7., Hyomandibular; .Q., Hyosuspensorial liga- 
ment; /zz., Intercalare; /.S¢., Interstapedial; ¥. Jugal; Z/, Lower labial cartilage; 
Mk., Meckel’s cartilage; JZx., Maxillary; J/z., Mandible; J7.S., Mesostapedial; 
0.C., Occipital condyle; P., Parietal; Parv., Parasphenoid; /g., Pterygoid; Pm., 
Premaxillary ; Pod., Postorbital arch; @Q., Quadrate; Q.C., Quadrate cartilage; S., Sz, 
Stapes; Sg., Squamosal; .S/., Superior labial cartilage; 7., Trabeculum; 7Z7y., Posi- 
tion of Membranum tympani. 
Cartilage, blue; ligament and membrane, yellow; bone, white. 
