D and D' show the fore and hind limbs, to illustrate their homology. D is in the embryonic position. The radius and tibia are, at an early stage in development, on the anterior edge of their respective limbs; the ulna and fibula, posterior; the former are spoken of as preaxial in position, the latter as postaxial. But in the adult the humerus is twisted so that the proximal end of the radius lies at the outer side of the elbow, whence it crosses the ulna, so that its distal end is inside, while the femur is also twisted round, so that the entire tibia is internal. Figures 1 and 2. -Limbs.-- a.c., acetabulum. acr., acromion. as., astragulus. c., carpus. ca., calcaneum. co., coracoid. [coty., cotyloid bone.] fb., fibula. fe., femur. g., glenoid cavity (for head of humerus). hd., head of femur. hum., humerus. i., ilium. is., ischium. m.c., meta-carpals. na., navicular. o., olecranon process of ulna. o.f., olfactory fossa. pb., pubis. r., radius. u., ulna. Figure 3. -Sternum.-- Mb., manubrium. r1., r2., and etc., sternal ribs. st., sternebrae. xi., Xiphisternum. Figure 4. Vertebrae.-- At., Atlas. Ax., axis. c., [b.] centrum. C.V., caudal vertebra. c.v., [Cer.V.] cervical vertebra. ep., epiphysis. f.r., fused rib (in cervical vertebrae). L.V., Lumbar vertebra. m., metapophysis (of lumbar vertebra). n.a., neural arch. n.s., neural spine. r., rib. S.V., sacral vertebra. [T.V., Thoracic.] tr.p., transverse process. v.a.c., vertebrarterial canal. z., zygapophysis. {Illustration: Diagram Sheet 5.} Sheet 6. The Skull of Canis.*-- 1. Dorsal. 2. Ventral. 3. Right Lateral Aspect. 4. Section a little to the left of the nasal septum. 5. Lower jaw (smaller) 6. Hyoid apparatus. {Lines from First Edition only.} -*A Fox in this case. The skull is quite like that of a Dog, but it has the advantage of more distinct sutures between the bones.- a.n., anterior nares. a.s., ali-sphenoid. b.h., body of the hyoid. b.o., basi-occipital. b.sp., basi-sphenoid. c., condyle of the skull. {c.1, c.4, canines.} c.f., condylar foramen (for XII.). c.h., cerato-hyal. E.f., Eustachian foramen. e.h., epihal. -e.n., or a.n., the anterior nares.- e.o., exoccipital. eth., ethmoid. e.t., ethmo-turbinal. f., frontal. f.l.a., foramen lacerum anterius. f.l.m., foramen lacerum medium. f.l.p., foramen lacerum posterius (for IX., X., XI.). F.M., or f.m., foramen magnum. f.o., foramen ovale. f.r., foramen rotundum. {i., incisors.} ju., jugal. m., molars. m.t., maxillo-turbinal. mx., maxilla. na., nasal. n.t., nasal turbinal. o.f., optic foramen. o.s., orbito-sphenoid. p., or pal., palatine. pa., parietal. p.m., pre-maxilla. p.m.1, p.m.4, premolars. p.n., posterior nares. p.sp., pre-sphenoid. pt., pterygoid. s.h., stylo-hyal. s.m.f., stylo-mastoid foramen (for VII.). s.o., supra-occipital. sq., squamosal. s.t., sectorial tooth. t.h. thyro-hyal. vo., -black line indicating position of- vomer. z.p., zygomatic process of squamosal. {Illustration: Diagram Sheet 6.} Sheet 7