22 MISS J. B. PROCTER OX THE SKULL AND 



bones overlie tlie subnnsal laminae and the adjoining border of 

 the ethmoid. The vomerine teeth are arranged in a simple line 

 of four, springing f)'om a prominent ridge on the outer oblique 

 edge of each bone. 



The fronto-2}arietals are strongly ossified, and somewhat rugose 

 on the anterior surface. The sagittal suture commences almost 

 at their anterior extremities, but does not persist beyond a third 

 of their length. Their combined width, anteriorly, is about a 

 quarter of their length. At the postero-innei' corner of the orbit 

 they form small sharp projections, and then reach double the 

 width. Posteriorly there is a slight sagittal crest, with two 

 oblique lateral wings which form the commencement of the 

 mastoid processes. 



The parasphenoid is of the usual dagger shape, but I'ather 

 more shapely than that of E. temporaria, and has an extremely 

 tapering point. The lateral limbs of this bone are partially 

 hidden beneath the superimposed inner limbs of the pterygoids. 



The cartilage- bones of the cranium. 



The ethmoid, a.s compared to that of B. temporaria, is elongated. 

 In the specimen figured it is almost one-half the length of the 

 entire skull. Anteriorly it is trilobate, or fleur-de-lys-shaped ; 

 dorsally this portion is overlain by the nasals, and ventrally the 

 central lobe is partially obscured by the vomers and the proximal 

 ends of the palatines. The main tubular portion of this bone, 

 which reaches almost to the optic foramen, is covered by the 

 fronto-parietals, but is visible on the ventral side through the 

 semi-transparent parasphenoid. As already stated, only a minute 

 diamond-shaped area of the ethmoid is exposed to view on the 

 dorsal surface, where it is bounded by the postero-median notch 

 between the nasals anteriorly, and by the antero-median notch 

 between the fronto-pai^etals posteriorly. In the antero-inner 

 cornier of the orbit the ethmoid is pierced on each side by a small 

 foramen for the orbito-nasal nerve. 



The prootics. — The dorsal surface of each is lai-gely covered by 

 the inner branch of the squamosal, and its inner borders underlie 

 the fronto-parietals. In the anterioi- wall below the flange of the 

 fronto-parietals is the foramen for the fifth and seventh cranial 

 nerves. The prootic forms the roof and the anterior wall of the 

 auditory capsule. 



The exoccipitals meet each other in the median line both dor- 

 sally and ventrally. The prootic-exoccipital suture proceeds along 

 the crest of the mastoid process ; the fronto-parietal-exoccipital 

 suture is difficult to trace. "Ventrally the anterior borders of 

 these bones are bounded by the parasphenoid. The exoccipital 

 condyles are well developed, and are visible fi'om three aspects ; 

 at the base of each are two foramina, the iipper minute and the 

 lower larger and internally divided ; tliese give exit to the ninth 

 and tenth cranial nerves. 



