:' IiMi ' 



Crjiptozoon a}ul other Ancient Fossils. 



205 



;iii 



haiiada, 



coiK'oiitiio lines, in Nvi'll-idcseivi'd s|te('iiiUMis, is traversed 

 liy numerous minute irrej^ular eaiuils, which hraneh and 

 anastomose witiiout rej^ndarity. The central jH.i'tions of 

 the masses are usually Idled with crystalline, onmular 

 and oolitic material, and many specimens show the 

 intrusion ot these extraneous and inorganic substances 

 between the concentric lanuna-." 



In general foi'm the masses are hemispherical or broadly 

 turbinate, and the layers are concave upward as if they 

 had grown from a central i)oint or circle and expanded 

 very rapidly in ascending, the general result resendjling a 

 series of bowls one within another. The larger masses 

 are from one to two feet in diameter. 



Thin slices, from sjtecimens kindly presented to the 

 Peter Hedpath ]Museum by ]*rof. Hall, show that the 

 priniiiry lanuntxi are thin and apparently carbonaceous, as 

 if originally of a corneous or membranous character, and 

 they are usually finely crumpled as if by lateral pressure,' 

 while they can occasionally be seen to divide into two 

 lamina' with intervening coarsely cellular structure. The 

 tliick intermediate layers which separate these primary 

 lamina' are composed of grains of calcareous, doloniitic and 

 silicious matter, in some specimens with much fine car- 

 bonaceous material. This last, under a high power in thin 

 slices, is seen to present the appearance of a fine network 

 or stroma in which the inorganic particles are entangled. 

 The canals traversing these intermediate layers appear to 

 be mere perforations without distinct walls, and are tilled 

 with transparent calcareous matter, which renders them, 

 luuler a proper light, sufficiently distinct from the grey 

 granular intermediate matter which they t ..verse. So 

 far as observed, the canals are confined to the intermediate 

 layers, and do not seem to penetrate the primary lamina?, 

 though these sometimes present a reticulated appearance 



1 Tliis limy, however, rejiresent an originally eorrugatetl structure of the hiiuina;. 









