THE SKULL THE CRANIUM 305 



of the anterior wall of the oblique cleft which divides this surface into 

 two parts (Fig. 222). The inner aspect of the piece (Fig. 227) is 

 rudely triangular ; it exhibits, above, the oval scroll m', then the 

 oblique edge of the partition m, then a depressed area m", as already 

 described (p. 299), limited below by a sinuous, elevated line. Only 

 this much of the surface is visible on the inner aspect of the lateral 

 ethmoid. Below this elevated line is a triangular lower area which 

 fits over the depressed middle part of the outer surface of the fourth 

 piece. Below this area, on another and external plane, is seen the 

 strongly concave inner surface of the cleft plate. (Compare Fig. 221.) 

 The outer surface of the mesial piece (Fig. 228) consists of two 

 parts : an upper, sickle-shaped body and a lower, curved cleft plate, 



FIG. 228. 



Opposite Lower Part of Inner Surface of First Piece. 



Attachment to Cribriform 

 Plate. 



. Opposite Lower Part of Inner Surface 

 Partition, m. c^tifif ^Jm ,< iif y f Second Piece. 



Cleft Plate. 

 MESIAL PIECE OF LATERAL ETHMOID, OUTER ASPECT. 



standing outward at right angles to it (Fig. 221). The upper portion 

 is for the most part flattened ; near the upper anterior end are a promi- 

 nence and a depression which follow a depression and a prominence 

 on the inner surface of the first piece (scroll 1') ; a still lower depres- 

 sion, with a line continued upward and backward from its upper edge 

 close to the lower border, marks the area opposite the upper part of 

 the inner side of the second piece (2'). All this part of the mesial 

 piece is separated from the cleft plate by a deep excavation which 

 forms the upper half of the bottom of the ethmoidal cleft. The 

 outer edge of the cleft plate is attached to an oblique ridge on the 

 inner surface of the maxillary bone, extending down to the lachrymal 

 opening. 



The third piece (Fig. 229) forms the fourth and fifth outer scrolls 

 (3', 3") ; it is much smaller than the second piece, and more flattened 



from side to side on the outer surface. Both scrolls are distinct ; the 



20 



