DEVELOP JIEXT OF THE SKULL ES' TIIE UEODELES. 213 



PLATE XXXIX. 



Fig. 1. Siren lacertina : adult. The skull, side view, X 4 diam. 



Fig. 2. The same : young specimen. The endocranium, upper view, X 5^ diam. 



Fig. 3. The same: adult. The lower arches, upper view, x4 diam. 



Fig. 4. Menopoma alleghaniensis : adult. The lower arches, left side, upper view, 



X 2 diam. 

 Fig. 5. The same, auditory region of the skull, outer view, x 4 diam. 

 Fig. 6. The same, auditory region of the skull, oblique view, X 2 diam. 



PLATE XL. 



Fig. 1. Lissotriton punctatus: larva, ^ inch long. The skull, upper view, X24 diam. 



Fig. 2. Triton cristatus : larva, 2^ inches long. The skull, upper view, x 7^^ diam. 



Fig. 3. The same, lower view, X 7|- diam. 



Fig. 4. Part of the same, upper view, X 14f diam. 



Fig. 5. The same largest larva, 2 in. 11 lines long, the lower arches, upper view, 



X 7| diam. 

 Fig. 6. The same : a more advanced lai-va, with gills almost absorbed, 2^ inches long. 



The skull, upper view, x75 diam. 

 Fig. 7. The same, lower view, X 7^ diam. 



PLATE XLI. 



Fig. 1. Triton cristatus: adult. The skull, upper view, X 6 diam. 



Fig. 2. The same, lower view, x 6 diam. 



Fig. 3. The same, side view, XG diam. 



Fig. 3 a. The same, right mandible, inner view, x 6 diam. 



Fig. 4. The same, endocranium, upper view, X 6 diam. 



Fig. 5. The same, horizontal section of the nasal region of the skull, upper view, 



X6 diam. 

 Fig. 6. The same, suspensorium, lower view, X 12 diam. 

 Fig. 7. The same, the lower arches, upper view, x 6 diam. 

 Fig. la. The same, thyrohyal of a younger specimen, upper view, xG diam. 



LIST OF AiBEEVIATIONS. 



The Roman figures in the Plates indicate the nerves or nerve-foramina 



a. p. Ascending process. b.hr. Basibranchial. 



ar. Articulars. h.hy. Basihyal. 



ar. c. Articular condyle. C"'^. Cerebrum (fore and mid brain). 



a. s. c. Anterior semicircular canal. c-^^!/- Ceratohyal. 



a. tr. Apex of trabecula. est. Cephalostyle. 

 au. Auditory capsule. 



