BIHANG TILL K. SV. VET.-AKAD. HANDL. BAND 18. AFD. IV. N:0 1. 59 



into separate lamels, fig. 70, 71. Tliis is manifest in the 

 dorsal as well as in the ventral aspect of the middle body. 

 On either side of its mesial ridge, Pl. VII, fig. 57, 58, a suc- 

 cession of beams is seen to divaricate, some thick and strong, 

 others more slender and less distinct, all imbedded in a fibrous 

 mäss of looser consistence. Along a line marking, above, the 

 half breadth of each half-pyramid, and, below, its marginal 

 third part, the connecting mäss disajtpears, its strings forming 

 delicate bows between the beams and interlacing, and the 

 beams, partially bifnrcated, stånd forth as the upper and un- 

 der edges of lameliar partitions arranged fanlike, fig. 52, 59, 

 60, all around, from the lower labial process to beyond the 

 upper, supra-alveolar, process. The laterally produced com- 

 pact middle body from which they issue, presents an upper, 

 broader, sloping support and a lower more narrow, and where 

 both meet, Pl. VIII, fig. 66, rh., they form a rachis, of a dense 

 texture, from which tlie lamels radiate, fig. 5.9, rh, like the 

 vanes from the shaft, the upper ones large, the lower smaller. 

 They extend laterally till they reach one of the five planes 

 that divide the dental står into the live pyramids. Close be- 

 fore attaining that plane, every lamel, upper and lower, is 

 parted into a series of short branches, fig. 71, which diverge 

 right and left, while, by repeated ramification, they subdivide 

 into branchlets that spread out, fig. 72, and give rise to the 

 layers of closer and closer net-work, whicli constitute the thin 

 but strong calcareous sheet that affords to the inter-pyramidal 

 muscles their attachments and their insertions. Outside, the 

 direction of each lameilar partition is made apparent tlirough 

 a slight and narrow elevation, Pl. VII, fig. 59, and a series 

 of noles, plaees of exit for the vascular and nervous systems 

 supplying the muscles. There seems to be one hole for every 

 lobe, and at the rachis as many larger holes as there are di- 

 varicating branches. 



In consequence of the radiate disposition of the j»artitions 

 the lateral inter-muscular sheet, which is the result of their 

 repeated divisions, attains a great expansion, widely surpas- 

 sing, all around, the area of the symphysis, fig. 52, 60. Its 

 outline, fig. 59, is upon the whole sub-elliptic, sonewhat leng- 

 thened and broader exteriorly. Its inner, alveolar part, the 

 interiör wing, al. int., fig. 52, 59, 60, the representative of the 

 whole inter-muscular surface in the Regularia, is very small; 



