404 MR. ST. GEORGE MIVART AND DR. J. MURIE [June 26, 



The pronator quadratics is very extensive, having attachments to 

 the shaft of the radius aud ulna for nearly their whole length, and 

 not for half only as Meckel says*. But at the same time he also 

 states that it is found in some other Rodents in the same condition 

 in which we find it in Dasi/procta cristata. 



In the Guinea-pig, Hare, and Rabbit this muscle is very small, 

 from the approximation of the bones. 



The extensor carpii radialis lonyior arises from the humerus above 

 the external condyle ; its fleshy belly extends about halfway down 

 the forearm, and ends in a tendon which is inserted into the proxi- 

 mal end of the metacarpal of the index (fig. 3, E. c. r. I. and b.). 



There is no difference in the Guinea-pig, Hare, and Rabbit. 



The extensor carpii radialis brevior arises beneath the last, and is 

 inserted into the radial side of the metacarpal bone of the third digit 

 (fig. 3, E. c. r. I. and b.). 



The same in the Guinea-pig and Hare ; the muscular bellies in 

 all are very closely applied. 



The extensor communis digitorum has origin from the external 

 condyle, the muscle being strongly tendinous beneath. Passing 

 downwards it divides into three separated tendons, which are respec- 

 tively inserted into the second, third, and fourth digits. There is a 

 second part, which gives rise on the ulnar side to a much more deli- 

 cate tendon, which passes down beneath the tendon of the other part, 

 and, dividing, goes to the third and fifth digits. 



Meckel f remarks that in the Marmot there are two extra extensor 

 muscles which supply the third and fourth digits. 



In the Guinea-pig it is as in the Agouti, except that the tendons 

 of the larger part are inserted into the third, fourth, and fifth digits ; 

 while the smaller part sends two tendons to the index and third 

 digits respectively. 



In the Hare this muscle sends four tendons — namely, to the index 

 and the three outermost digits ; that going to the fifth digit forms a 

 muscular belly rather distinct from the rest, and which appears to re- 

 present the smaller part above described in the Agouti and Guinea-pig. 



The extensor carpii ulnaris springs from the external condyle and 

 the contiguous part of the ulna ; its insertion is into the base of the 

 fifth metacarpal bone (fig. 3, E. c. u.). 



Alike in the Guinea-pig and the Hare. 



Extensor ossis metacarpii pollicis. This is a very large and strong 

 muscle, with an exceedingly broad tendon. It arises from the conti- 

 guous surfaces of the radius and ulna, and is inserted into the base 

 of the metacarpal bone of the pollex (figs. 2 & 3, E. o. m.p.). 



In the Guinea-pig it is similar, except that its tendon (the pollex 

 being absent) runs on to the base of the metacarpal of the index, 

 though mainly inserted into the rudimentary trapezium. 



In the Hare, as in the Agouti, the tendon goes to the metacarpal 

 bone of pollex. 



Both the extensor primi internodii and extensor secundi internodii 

 pollicis are absent in the Crested Agouti and in the Guinea-pig. 

 * Luc. cit. p. 302. I Loc. <-it. p. 3-22. 



