The two distal tarsal bones are small; one is said by Reynolds to represent the first three tarsalia (t³), the other (t⁴⁻⁵) the fourth and fifth. Wiedersheim says one of these bones represents the first three tarsalia, the other the fourth. In the tarsus here shown these two elements are fused.
The foot has five digits, though the fifth is small and consists merely of a small, distally pointed metatarsal bone. According to Wiedersheim this fifth metatarsal is fused with the fifth tarsalia. The metatarsals of the first four digits are long and progressively more slender from the first to the fourth; each is distinctly enlarged at the ends. The first digit or hallux has two phalanges, the second has three, the third has four, and the fourth has four. According to Reynolds, the fourth toe has five phalanges; the figure here shown, which was drawn from nature, has only four on the fourth toe; the latter is the number given by Bronn for the crocodiles. The terminal phalanges of the first three digits are large and pointed, with the same lateral grooves noted in connection with the fore foot; each is sheathed in a horny claw. The four fully developed digits of the pes are nearly twice as long as the corresponding digits of the manus, but they are not proportionately thicker.
CHAPTER III
THE MUSCLES
The description of the muscles here given is taken from Bronn ([11]), who, in turn, largely follows Gadow. The animal described is the crocodile, but while Bronn does not indicate the species, it is probable that the differences between the various members of the Crocodilia would be slight. The figures of the muscular system are mainly from the Florida alligator.
In his description Bronn gives for each muscle the various synonyms (often more than half a dozen) that are employed by different writers; in this work Bronn’s nomenclature is given first and the synonyms follow in parentheses.
The Chewing Muscles
Temporalo-maxillaris (Temporalis) (Masseter, Temporal, Aeussere ober Heber or Schlafmuskel). Arises in the temporal fossa, passes under the zygoma, and inserts itself on the inner and outer sides of the lower jaw.
Pterygo-maxillaris (Pterygoideus) (Pterygoidien, Aeusser Flügelmuskel, Pterygoideus externus, Pterygoideus internus). A large muscle which consists of two portions: the outer, weaker portion springs from the pterygoid process, the inner stronger part from the pterygoid fossa and pterygoid process; they run together around the angle of the lower jaw, where they form a large, bulging fold. They are the chief muscles of this part of the body since the masseter is lacking and the temporalis is weakly developed.
Occipito-maxillaris (Digastricus maxillæ) (Niederzieher des Unterkiefers, Abaisseur ou l’analogue du digastrique, Senker des Unterkiefers, Aristotelis apertor oris, Digastricus, Aperator oris). Arises from the hinder border of the lateral occipital and is inserted at the hinder end of the lower jaw. Its course is from front to back. If the skull be stationary this muscle drops the lower jaw; if the jaw be fixed it raises the skull.