Miscellaneous. 457 



the head in that and other species of Teleosaurus from British strata, 

 especially of remarkably perfect skulls obtained by H. Moore, Esq., 

 from the Lower Oolite of Somersetshire. 



The following is the cranial structure in the Teleosauri, according 

 to my present knowledge. 



The occipital region, as in modern Gavials, is very broad in pro- 

 portion to its depth. The foramen magnum is the sole vacuity in its 

 bony wall, and is bounded by the ordinary occipital elements ; the 

 hind surface of the skull is completed by the parietal, the mastoids, 

 and the tympanies. 



The basioccipital developes the main part of the condyle, which 

 forms somewhat more than the lower half of a hemisphere ; the two 

 upper angles being contributed by the exoccipitals. Near the upper 

 part, which enters in a small degree into the formation of the great 

 foramen, the condyle usually shows a small central pit. Below and 

 in advance of the condyle, the basioccipital expands and bifurcates 

 into two very short and thick diverging hypapophyses with rough 

 truncate terminations ; their bases converge forwards, forming the 

 sides of a deep groove, at the fore part of which are two orifices lead- 

 ing to air-cells in the basioccipital. 



The broad extended bases of the exoccipitals articulate with the 

 sides of the condyle and of the hypapophyses of the basioccipital, 

 and, after a slight contraction, each exoccipital rapidly expands and 

 branches into three short and broad processes. The upper and inner 

 one curves upwards and inwards to complete the periphery of the 

 foramen magnum by uniting with its fellow above that aperture. The 

 second extends outwards, and forms the compressed horizontal plate 

 articulating with the lower and hinder part of the ridge of the mas- 

 toid : a vascular foramen and a deep and smooth notch divide this 

 from the lower and third process, which represents the paroccipital : 

 this part articulates by a broad overlapping sutural surface with the 

 tympanic. 



The groove dividing this surface from the paramastoid process is 

 the back part or wall of the meatus auditorius. 



The exoccipital thus articulates with its fellow and the super- 

 occipital above, with the basioccipital below, and with the mastoid, 

 alisphenoid and tympanic externally. Its internal surface is smoothly 

 excavated, posteriorly, for the epencephalic cavity, and irregularly 

 excavated anteriorly for the acoustic cavity. The epencephalic sur- 

 face is perforated by small foramina for the roots of the ninth nerve. 

 The superoccipital is a depressed transversely extended bone, with 

 an outer vertical subrhomboid surface : it articulates by broad su- 

 tures to the exoccipitals below and to the parietal above : the under 

 surface, in advance of the exoccipital suture, is smoothly and deeply 

 excavated, to form the roof of the epencephalic chamber ; the sides 

 of the bone are excavated by sinuses from the acoustic chamber. 



In regard to the occipital elements, the Teleosaur differs from the 

 Gavial in the division of the hypapophyses, and hereby more resem- 

 bles the Lizards than the Crocodiles, in which the two processes are 

 blended together in a thick descending mass : the paroccipital is 



