652 DR. p. OHALMBKS MITCHELL ON THE [DeC. 17, 



my present knowledge I am inclined to think that that head 

 is a separated pcrtion o£ the femoral insertioii of the caud-ilio- 

 fiexorius ; and that therefore the B-alline type is more archecentric 

 in this respect than the type of Otis. But however further 

 knowledge may lead us to interpret this, it is again plain that the 

 specialization of the different members of the Gruiform assemblage 

 has proceeded on lines of considerable independence. 



Ilio-fihidaris. — In most of the Gruiformes this muscle (text- 

 fig. 79, IL.-FIB.) in its origin, passage through a sling at the knee, 

 and insertion to the iibula is similar to the condition found in the 

 majority of Avian groups. Beddard (1) has described a peculiarity 

 of insertion in the Heliornithidae ; in Podica there are, in addi- 

 tion to the normal insertion, a second insertion to the leg and an 

 insertion to the fascia covering the gastrocnemius. The latter 

 insertion he found also in Heliomis, but in my specimens of that 

 bird it was represented only by a very slight band of fascia devoid 

 of muscular fibres. Such additional insertions plainly are apo- 

 centrie modifications. I have found the gastrocnemial insertion in 

 the Ostrich and in some Anatidae, and it has been described in the 

 case of the Alcidae. It is a multiradial apoceutricity, and there is 

 to be noted about it only that among the Gruiformes it occurs in 

 eutaxic forms. 



Isehio-femoralis (obdurator extermis), Ohdurator (ohdurator in- 

 ternus)^ Accessorii ohduratoris (gemeJli). — In all these are present, 

 but I have no peculiarities to note. 



Piib-ischio-femoralis (adductors). — In most of the Gruifoi'mes 

 both adductors are present, and in these cases the superficial 

 adductor is entirely fleshy and is much narrower than the deep 

 adductor. The latter is wide and strong in all but the Eallidse 

 and ITelioruithidae ; in Otis (text-fig. 83, P.I.F) and in Earypyga 

 it shows an attachment to the middle head of the gastrocnemius. 

 In the Eallidse it shows tendinous degeneration, in many forms 

 being reduced to a thin although wide sheet of fascia. In the 

 Heliornithidae (at least in Heliomis, text- fig. 84) only one of the two 

 muscles is present, and this muscle is entirely fleshy and very 

 narrow. It appears to be the superficial muscle, the representative 

 of the deep muscle, which in the Sails is tendinous, having been 

 lost. It is to be noted that this apocentricity occurs in a eutaxic 

 form. 



Tibialis anticus, Popliteus, Extensor digitorum communis., Peroneus 

 superficialis (with slip to the perforated flexor of digit iii.). — These 

 are all present and practically identical in the Gruiformes, the 

 tibialis anticus passing through only a fibrous bridge. 



Peroneus profundus. — This muscle is present and strong in all 

 the Gruiformes except the Arauiidse, Dicholophidae, and Otididse. 

 I am able to coiToborate Gadow's statement that it is absent in 

 Otis. I found no trace of it in Aramus and in Cariama, but 

 Beddard (1) affirms its presence in the Dicholophidae. The 

 absence must be regarded as an apocentric modification, and the 

 incidence of this is not correlated with eutaxy and diastataxy. 



