Eig. 15. The right malar hone, outer surface: o. p., orbital process.
„ 16. The inner surface of the same bone.
„ 17. The left maxillary, premaxillary and nasal bone in opposition and seen
from the outside.
„ 18. The aspect of the same bones, also well showing the very characteristic
overhanging maxillary, &c. The same lettering applies to this and fig. 17:
<?., crest; n., nasal bone; pmx., premaxillary; mx., superior maxillary
bone.
„ 19. The left mandible, its exterior surface; c., condyle; a ., angle; g o ., coronoid
process; f., pointing to two foramina.
,, 20. Left moiety, seen from below, of the hyoid arch: bh., basihyal; th., thyrohyal,
sh., stylohyal; ch., ceratohyal. The letters point to the bony elements,
all the other pieces being cartilaginous.
PLATE XLI.
Eig. 1. A cast of the cochlea, nerve tracts, and semicircular canals of Platanista
gangetica. Their natural size.
„ 2. The opposite side of the same preparation.
„ 8. Drawing of a cast of the semicircular canals of Platanista, enlarged three
diameters.
„ 4. A cast of the cochlea, nerve tracts, and semicircular canals of Orcella
brevirostris. Their natural size.
„ 5. The opposite side of the same preparation.
„ 6. Sketch of the semicircular canals of Orcella brevirostris. Enlarged three
times natural size from the preceding specimen.
7. A cast of the cochlea, nerve tracts, and semicircular canals of the genus
Olobiocephalus. Natural size.
„ 8. The opposite side of the same preparation.
9. Its semicircular canals enlarged three times natural size.
10. View cast of the cochlea, nerve tracts, and semicircular canals of Monodon
monoceros. Of natural size.
11. The opposite side of' the preceding preparation of the narwhal.
12. Semicircular canals of Monodon, enlarged three diameters.
13. Left scapula of the Gangetic Dolphin Platanista gangetica; its outer
surface: g., glenoid concavity; a., acromion process; c., rudimentary
coracoid process.
14. Dorsal aspect of the bones of the left forearm and manus of Platanista;
reduced. The lettering applies as follows : h., humerus; r., radius; u.,
ulna.; tm., trapezium; rd., radiale or os scaphoid; o. i.f os intermedium or
lunare; td., trapezoid; mg.,' os magnum; c. u., cuneiform and unciform;
m, the metacarpals; I, II, III, IV, V, digits.
Eig. 15. Upper surface of the two last dorsal and the first lumbar vertebra of Platanista
gangetica; reduced from nature: X and XI, segments of
the tenth and-eleventh ribs; t., transverse process of the first lumbar
vertebra.
16. Outlines in a reduced scale of from I to X of the ten foremost ribs from
the right side of P. gangetica.
PLATE XLII.
The characteristic parts of the skeleton of the Irawady Dolphin Orcella
fiimmalis, Anderson. Eigures all considerably reduced from their natural dimensions—
Eig. 1. The cranium in side view, \ natural size.
2. The superior aspect of the same skull, \ natural size.
3. The lower base of the same skull, ^ natural size.
4. Eight mdiety of the hyoid arch, \ natural size: bh., basihyal; th., thyrohyal
; ch., ceratohyal; sh., stylohyal.
5. Eifth cervical vertebra, 4 natural size.
„ 6. Eirst dorsal vertebra, „ „
„ 7. Seventh dorsal vertebra, >, »
„ 8. Eirst lumbar vertebra, „ „
9. The forearm and manus; h., humerus; r., radius; u., ulna, \ natural
size.
10. The thirteen ribs seen from the outside, ^rd natural size.
„ 11. The right pelvic bone, seen from in front, frd natural size.
PLATE XLIII.
A comparison of some of the bones of O r c e l l a jlvmmalis and of O. brevirostris—
. ,
Eig. 1 Left scapula of O.fliminalis, Anderson; its outer surface, i natural size.
„ 2. View of glenoid cavity of the same bone, \ natural size.
„ 3. Atlas and aris of O. fivmi/nalis,. seen from in front, ^ natural size.
4. Eight tympanic bone, &c., of 0. jfhminalis; its interior face and of natural
size. Natural size.
,, 5. Sternum of O.fluminalis, natural size.
6. Left scapula of Orcella brevirostris ; its outer surface, ^ natural size.
7. Glenoid concavity of same scapula, ^ natural size.
8. Atlas and axis of O. brevirostris, seen from in front £ natural size.
” 9. Eight.tympanic bulla of Orcella brevirostris, the interior face of natural
size. ' Natural size.
10. Sternum of O. brevirostris, its inner aspect, \ natural size.