198 ON THE LATE PROF. GARROD'S CONTRIBUTIONS 



this paper, only stating here that species of the same genus and nearly 

 allied genera have, nearly in every case, the same myological formula, and 

 that \-D. families peculiarities involving more than one change are rare, 

 farther differences indicating a more remote relationship. 



V. The Distribution of the Deep Plantar Tendons*. 

 In all birds, whatever number of toes they have, there are two deep 

 flexor muscles of the toes, the fleshy bellies of which are situated 

 between the knee and the " ankle," whilst their tendons run along the 

 posterior aspect of the tarso-metatarse. One, arising from behind the 

 external condyle of the femur, is the flexor longus hallucis ; the other, 

 arising from the posterior aspect of the tibia and from the fibula, is the 

 flexor perforans digitorum, so called because its terminal tendons per- 

 Ibis, 1881, f orate those of the more superficial flexor perforatus (the muscle, it will 

 p. 13. j^ remembered, joined by the tendon of the ambiens). Below the 

 " ankle " the tendons of these muscles run along the tarso-metatarse ; 

 whatever their ultimate distribution, they may be easily identified in 

 this region, the^m^r longus hallucis being always external to, or super- 

 ficial of , the flexor perforans (or both). In all the Passeres, as already 

 noticed by Sundevall (except in the Eurylaemidse, vide infra), as well as 

 in Upupa epops and perhaps one or two Ardeine birds, these two tendons 

 are quite independent of each other, so that if the flexor hallucis be 

 artificially pulled no flexion (closing) of the other digits takes place. 

 This arrangement is represented in fig. 6. In all other birds, however, 

 the two tendons, during some part of their course in the tarso-metatarse, 

 are more or less intimately connected together by a fibrous band or vin- 

 Ibis, 1881, culum, or may even completely blend. It is to a consideration of the 

 p. 14. varying arrangements produced that this paper of Prof. G-arrod's is in 

 the main dedicated ; and some of the most important modifications may 

 be noticed here. 



In a large number of birds the type presented by the common Fowl 

 obtains. Here the flexor perforans supplies digits II-IY, and t~he flexor 

 hallucis only digit I (the hallux) ; this, as it crosses the tendon of the 

 flexor perforans, sends down a strong fibrous vinculum (vide fig. 7, V). The 

 proportions of the vinculum to the main tendon (that distributed to the 

 hallux) vary greatly, as it may or may not be greater than the hallucial 

 portion. In some Birds of Prey a vinculum may be combined with a 

 special slip of tendon to digit n, or it may be nearly entirely distributed 

 to that digit. In the Cathartidae a quite different arrangement, next to 

 be described, obtains. Here, and in many other birds, particularly 

 amongst the Anomalogonatce, the two tendons blend completely, and the 



* " On the Disposition of the Deep Plantar Tendons in different Birds," P. Z. S. 

 1875, pp. 339-348. 



