322 



ZOOLOGY 



SECT. 



ii.. '.m;4.— Carpus of Iiacerta 

 agilis, (left) from ubuve. li. 

 radius ; U. ulna ; c. ceiitrale ; 

 i intermc iium ; v. radiale ; v. 

 ulnare : 1—5, the five distal 

 carpals : t, insiforni ; / — V, the 

 five metacaipals. (From Wieder- 

 sheim's Comparative Aiuitoin;/.) 



convex articular surface for the carpus. The carpus (Fig. 964) is 



composed of ten small polyhedral or rounded carpal bones. These 



consist of a proximal row containing 

 three, viz., the radudc (/■), ^dnarc {it), 

 and intermedium (i), of a centrale (c), 

 and of a distal row of five (1-5) ; with an 

 accessory or plsifonn (-j-) bone attached 

 to the distal epiphysis of the ulna on its 

 post-axial side. The first digit or poJkx 

 consists of a metacarpal and two phal- 

 anges, the second of a metacarpal and 

 three phalanges, the third of a meta- 

 carpal and four phalanges, the fourth of 

 a metacarpal and five phalanges, and the 

 fifth of a metacarpal and three phalanges. 

 The number of phalanges in the first 

 four digits is, therefore, one more than 

 the serial number of the di^it. 



The pelvic arch (Fig. 965) consists of 

 two triradiate bones, the osna innominiata, 



each ray being a separate bone. On the outer side at the point 



from which the rays diverge is a concave articular surface — the 



acctahidum {Ac)—{ov the head of the femur. From the region 



of the ace tabu hnn 



one of the rays, 



the ilium (7), a 



compressed rod, 



passes upwards and 



backwards to arti- 

 culate with the 



sacral region of the 



spinal column. A 



second ray — the 



pubis (P) — passes 



downwar(is and 



forwards to meet 



its fellow in the 



middle line, the 



articulation bein«f 



termed the ^/?t/>/r 



symphysis. In the 



middle line in 



front, between the 



anterior ends of the 



pubes, is a small nodule of calcified cartilage, the cpipuhis {Cep)). 



The third ray or ischium (Is) runs downwards and backwards, and 



articulates with its fellow in the ischiatic symphysis, the ventral 



Fl<;. He.j.— Pelvis (,f I.acerta Vivipara, from the ventral .side. 

 Ar. aeetaljiilum ; Cip. epi-pubis. Fn'. foramen for obturator 

 n'irve (obtu:ator foramen); I[p. h. hj po-isehium ; /. ilium; 

 1 1, proeess representing the pre-aeetabular part of the ilium ; 

 h. ischium; P. pubis; PF. prc-pnbis. (From Wiedersheim's 

 C'omparatire A aalomii.) 



