THE MUSCULAR ANATOMY AND THE RESTORATION OE THE TITAN OTHERES 



717 



above mentioned, but also to the adductor minimi 

 digiti, the adductor indicis, and the adductores digi- 

 torum medii et quarti. The spaces between the proxi- 

 mal ends of adjacent metacarpals gave rise to the dorsal 

 interossei, while the depressions on the posterior aspect 

 of the proximal portion of the metacarpals served for 

 the origin of the palmar interossei which were inserted 

 ■ into the sesamoids, the latter being attached by liga- 

 ments to the proximal phalanges. The inner and 

 outer sides of the metacarpals show distally deep 

 lateral pits, one on either side of the facets for the 

 phalanges; these pits were for the collateral ligaments 

 that passed to the first row of phalanges and were 

 inserted on their proximal inner and outer expansions. 



The palmar surfaces of the first row of phalanges 

 were covered by the flexor digitorum profundus. The 

 lateral protuberances at the proximal ends probably 

 served for the collateral ligaments, while pairs of 

 proximal palmar rugosities probably served for the 

 ligaments of the sesamoids. At the sides of the 

 proximal phalanges may have been attached the ad- 

 ductors of the digits and the lumbricales (accessory 

 flexors arising from the tendon of the flexor sublimis). 

 Toward the distal end the lateral pits were probably 

 for the collateral ligaments, whUe the protuberances 

 above them probably gave attachment to the flexor 

 sublimus. 



The second row of phalanges (fig. 656) gave insertion 

 to the forked flexor profundus in the midpalmar surface. 

 The dorsal surface of the second phalanges gave in- 

 sertion to the extensors of the digits. The distal or 

 ungual phalanges gave insertion on their dorsal sur- 

 faces to the extensors and on their palmar surfaces to 

 the flexor sublimis. The distal roughening for the 

 hoof indicates a relatively small hoof in comparison 

 with the tapir and rhinoceros. 



The whole palmar surface of the manus was prob- 

 ably covered superficially by the flexor brevis manus, 

 as in the tapir. 



MUSCLES OF THE HIND IIMB 



[See PI. XLIV, B] 

 MUSCULAR ATTACHMENTS OF THE SACRUM 



The sacrum was securely fastened to the flium by a 

 system of iliosacral ligaments probably similar in 

 essentials to those in Equus as figured by Schmaltz 

 (1909.1, Taf. 6) and consisting of (1) a dorsal ligament 

 (called by Schmaltz the ligamentum sacro-iliacum 

 dorsale breve) running along the tips of the sacral 

 spines and being inserted anteriorly into the dorsal 

 border of the sacral flange of the ilium; (2) a broad 

 ligament running from the lateral edge of the trans- 

 verse lamina of the sacrum obhquely upward and 

 forward to the posterior border of the sacral flange 

 of the ilium (ligamentum sacro-iliacum dorsale 



longum, Schmaltz); (3) a broad sheet of ligament 

 extending between the transverse lamina of the 

 sacrum, obliquely downward and backward to the 

 dorsal border of the ilium above the acetabulum 

 (spina ischiadicum) and to the dorsal border of the 

 ischium as far back as the ischial tuberosity (liga- 

 mentum sacro-spinosum et tuberosum. Schmaltz) ; (4) 

 a number of oblique ligaments springing from the 

 anterior dorsal edge of the sacral flange of the ilium 

 and running to the spines of the lumbar vertebrae. 

 The hgaments above described are of great impor- 

 tance both in tying the pelvis securely in place and in 



Figure 656. — Arrangement of the muscles of the flexor 

 surface of the manus of Mesatirhinus peiersoni 



Restoration of muscles based chiefly on dissection of the forefoot of a tapir 

 by Murie after the removal of the palmaris longus, lumbricales, and 

 parts of the flexor tendons (cut at x). One-third natural size. 



affording origin to several of the great muscles of the 

 loins, croup, and buttocks, as follows: No. 4 (above) 

 affords partial insertion to the longissimus dorsi; Nos. 

 1, 2, 3 conjointly afford origin for the gluteus medius, 

 gluteus maximus, and "biceps 1" (femorococcygeus) . 



MUSCULAR ATTACHMENTS OF THE PELVIS 



The pelvis of Palaeosyops is of the subgraviportal 

 type in which the ilium spreads widely and has its 

 superior border well rounded out rather than concave. 

 In correlation with this adaptation the area for the 

 gluteus medius on the dorsum of the ilium and that 

 for the iliacus on the venter of the ilium are both 



