SKELETON OF COMMON FROG. 8 1 



and lodges the posterior part of the spinal cord. The neural canal is often 

 open terminally. 



The shoulder-girdle is complete : and the glenoid cavity divides it into 

 a dorsal scapular, and a ventral coraco-clavicular, moiety. The former con- 

 sists of a broad semicartilaginous supra-scapula and an ossified scapula, 

 the latter of an anterior clavicular bar separated by a fenestra from a 

 posterior coracoid. Both clavicle and coracoid are Connected by cartilage 

 medianly to one another and to the corresponding parts on the opposite 

 side. In the middle line project (i) anteriorly a conical bone ending in a 

 cartilage plate the episternum or anterior part of the interclavicle : (2) 

 posteriorly a flattish bone with a cartilage disc, the hypo-sternum. 



The pelvis has the V-shape characteristic of Anura or tail-less 

 Amphibia. The long ilium trends backwards to a disc-like symphysis into 

 which it enters, and which is partly cartilaginous and partly formed by the 

 two ischia. The acetabulum is a deep cup. 



The fore-limb consists of a humerus, and of a radius and ulna fused 

 together, a furrow indicating externally the line of union. The elements 

 of the carpus are small and consist in the proximal row of a scaphoid 

 ( = radiale) and a cuneiform ( = ulnare): of a centrale displaced to the radial 

 side : and in the distal row of a trapezium ( = carpale i) carrying the thumb, 

 represented by a single bone: a trapezoid ( = cp. 2) carrying the second 

 digit, which in the male enlarges at the breeding season, and a single 

 element ( = cp. 3, 4, and 5?) carrying the remaining three digits. The long 

 hind-limb consists of a femur, and of a fused tibia and fibula, A long astra- 

 galus ( = tibiale) and calcaneum ( = fibulare) united at each end form the 

 proximal row of the tarsus. The distal row consists of a tarsal element 

 which carries a single bone, the extra digit or sixth toe ; of a fused meso- 

 and ecto-cuneiform ( = tarsalia, 2 and 3), while the ento-cuneiform (tarsale i) 

 and the cuboid (t. 4 and 5) are represented by ligament. The five ordinary 

 toes are present, the number usual in the hind foot of both Anura and 

 Urodela. 



As in the majority of Amphibians, the skull of the Frog has no basi- or supra- 

 occipital ; no basi- or ali-sphenoid ; and no epi- or opisth-otics. The palatine and 

 pterygoid bones are here membrane bones, at first lying on the surface of a cartilage 

 rod, not as in Teleostean fishes ossifications in the cartilage. The pterygoid however 

 invades the subjacent cartilage. The hyoid apparatus (Fig. 6) consists of a median 

 basi-hyo-branchial plate (Bh.) suspended to the skull by a slender hyoid arch 

 (St. h.). Behind the lower end of this arch a process represents the remains of 

 the two first branchial arches, or cerato-branchials (Br.) ; another process on the 

 posterior edge of the median plate represents the third branchial arch, or cerato- 

 branchial (Br 1 ) ; while ossifications represent the fourth arch, the so-called thyro- 

 hyal (B. hy.). The Eustachian tube (Eu.) passes between the ear-capsule and the 

 outer process of the pterygoid. 



G 



