141 
mity or coxal zone and limb as the divergent appendages of the 
occipital vertebra. As to the homologies of these parts, the Doctor 
postponed the consideration of them till another opportunity, and 
proceeded simply with the tarsus. This consists in Man and many 
mammals of seven bones, which are arranged in two rows; each row 
has developed from it one or more digital phalanges when most de- 
veloped; with the first row the thumb or great toe is developed, while 
the other toes having metatarsal and digital phalanges are connected 
with the anterior row or distal end of the tarsus, where the tarsal bones 
are fused or developed in a single bone. This is beautifully seen in 
many of the birds, especially the Cursores and Grallatores: in the 
Apteryx, as figured in the ‘Zoological Transactions’ by Prof. 
Owen, vol. iii. pl. 49, the tarsus is seen to consist of a single bone, 
terminating in three distinct knuckles, for the articulation with the 
metatarsal phalanges; while the thumb is seen with its different 
joints on the posterior and inner aspect, and in its natural position. 
This part of the leg has long been mistaken by ornithologists : Prof. 
Owen calls it tarso-metatarsal, and Dr. Melville views it as the meta- 
tarsal, which Dr. Macdonald asserts is surely more erroneous than 
even Prof. Owen’s view. 
«« The thumb or great toe very often disappears in the endoskeleton, 
but may sometimes be seen in the exoskeleton, as in the leg of the 
Horse and some other mammals, where the metatarsus is fused into 
a single or shank-bone, terminating in a single phalanx as in the 
Horse, or double phalanx as in the Llama. 
«« Dr. Macdonald also briefly alluded to the nomenclature adopted 
by entomologists and other annulose zoologists, and maintained, that 
if the nomenclature of the anatomist was to be appropriated by them, 
they were bound to use the terms anatomically ; and then submitted 
the following sketch of the homologies of the posterior leg :— 
Coxa = Cotylon. 
Trochanter = Femur. 
Femur = Tibia. 
Tibia = Tarsus and great toe. 
Tarsus = Metatarsus and phalanges. 
«« These homologies are easily traceable in all the six legs of the 
Entomoid classes, and also in the thoracic legs of the Crustacea, and 
are particularly well marked in the large claw of the Crab, where the 
lines and markings point out the metatarsal and digital phalanges, 
terminating in the large claw; where the thumb or opposable claw is 
jointed to what may be viewed as homologous to the tarsus, while 
the rest is the fused terminal phalanges.” 
The communication was also accompanied with a verbal explana- 
tion of the several diagrams exhibited. 
