EMERSON: ANATOMY OF TYPHLOMOLGE. 
55 
Ihjo -branchial Apparatus. 
The hyo-branchial apparatus is made up of a series of cartilagi¬ 
nous rods. In the mid-ventral line lie two short cartilages, the 
first and second basibranchials, the basal elements respectively of 
the first and second gill arches. The first or anterior basibranchial 
is short and thick, the second is half as long again and slender, 
with a slightly enlarged posterior end. From the anterior end of 
the first basibranchial spring the hyoid cartilages, the longest and 
thickest of all. These are attached distally by ligaments to the 
skull, their direction, like that of the mandible and of the branchial 
arches, being postero-lateral. Posterior to these are the branchial 
arches, the first of which arises from the posterior end of the first 
basibranchial and also touches the second basibranchial. It con¬ 
sists of two rods, a short proximal one, the first cerato-branchial, and 
a longer, slender distal one, the first epibranchial. The second arch, 
arising from the anterior part of the second basibranchial, is like the 
first arch but more delicate. The third arch is incomplete, having- 
only an epibranchial cartilage which springs from the posterior bor¬ 
der of the second epibranchial at its proximal end. Extending pos¬ 
teriorly from the posterior border of the third epibranchial, at its 
distal end, is a small raphe, the rudiment of the fourth branchial 
arch (Goppert, ’ 94 ; Wilder, " 96 ). No trace of the fifth branchial 
arch, represented in other forms by the laryngeal cartilage, appears 
here (v. infra sub Respiratory System). 
The distal ends of the three epibranchials are contiguous and are 
attached by the levator muscles to the dorsal region of the head, 
forming the supports of the three external gill bushes. The gill 
slits, of which there are three in this animal, open from the pharynx 
to the exterior, the first between the hyoid and the first epibranchial, 
the second between the first and second epibranchials, and the third 
between the second and third epibranchials. The number of gill 
slits is here different from the number in Proteus and Necturus, for 
they have but two. 
Although as a whole the apparatus is similar to that of the Pro- 
teidae, the size and position of the second cerato-branchial and the 
shape of the second basibranchial make it correspond exactly with 
the hyoid apparatus of the larval Spelerpes ruber. 
