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MR, W. K. PARKER OK THE STRUCTURE AND 
In Rcma pipiens there are two or three splint bones ( 'inter-suspensorials ) between 
the quadrate cartilage and the hind crus of the pterygoid bone. 
In some types (e.g., Ceratophrys, Calyptocephalus, Pelobates, and Nototrema ) the 
surface of the investing bones is ornate, and almost Ganoich 
The following endoskeletal and exoskeletal bones are constant throughout the 
“ Anura ” in the adult skull 
1. The ex-occipitals.* 
2. The prootics. 
3. The pterygoids. 
4. The articulars. 
5. The thyro-hyals. 
6. The parasphenoid. 
7. The nasals. 
8. The fronto-parietals. 
9. The premaxillaries. 
10. The maxillaries. 
11. The squamosals. 
12. The dentaries. 
The skull is always finished with cartilage, below (contrary to the Urodeles), and 
never finished with cartilage, above (as in the Sharks). 
The occipital condyles are always double, and quite distinct, often wide apart; but 
the occipital arch is not always restricted to a right and left bone; there may be a 
rudiment, above and below, of a median centre. 
The skull is always closed in front by the ethmoid (cartilage or bone) : it is at 
times very unfinished and membranous in the orbital region (e.g., Rappia bicolor, 
Camariolius tasmaniensis, and Acris Pickering ii). 
The whole (true) ethmoidal region is formed by the trabecuke and intertrabecula ; 
the nasal roofs are distinct cartilages at first (like the eye-balls and auditory capsules); 
their floor is formed by the trabeculae. 
F .—On the likeness and unlikeness of the skulls of the “ Urodela” and “Anura.” 
The difference between the skull of a Tadpole and that of a larval Urodele is very 
great from the first (see Phil. Trans., 1877, Plates 22-24). In the latter the tra¬ 
beculae largely embrace the huge cranial notochord, and are some time before they 
close in in front of the membranous space below the fore brain. They finish their 
cornua, in the internasal region, afterwards, and they do not finish the occipital floor; 
distinct parachordals appear there. 
The suspensorium is in them, at first, quite distinct from the trabecula, when it does 
coalesce it unites, first, with the wall of the skull, above the orbito-nasal nerve; in the 
Tadpole it is from the first continuous, as cartilage, below that nerve. Their ethmo- 
* Tlie prootics and ex-occipitals do not always arise from independent centres. 
