98 LOWER PENINSULA. 



Cyathophylloid family. The frequent fragmentary condition of 

 the specimens and the altering effects of petrification prevent, in 

 many instances, an exact identification of all the collected speci- 

 mens, for which reason I have restricted myself to the description 

 of those forms only of which I had satisfactory material for exami- 

 nation. 



The genus Cyathophyllum, which gave the name to the entire 

 large family, is not the primitive type form in which its first rep- 

 resentatives appeared ; the oldest forms of the Cyathophyllides 

 were of the less complicated structure of Streptelasma and of 

 Zaphrentis, which existed already in the lowest strata of the 

 Trenton period. Cyathophyllum and many other diversifications 

 of the type commence to appear in the upper Silurian beds. The 

 Devonian period was the time of their greatest development, and 

 after the carboniferous period we find the whole family extermi- 

 nated, leaving no representative in the periods subsequent to the 

 Permian strata. 



CYATHOPHYLLUM, Goldfuss. 



Simple or compound polyparia, each polyp cell surrounded by its 

 own perfect wall. Vertical lamellse well developed, forming con- 

 tinuous leaves through the whole length of the corallum, and ex- 

 tending to the centre, or near to it. The interstices between the 

 lamellae in the peripheral area (formed by the ascending walls of 

 the calyces) are divided into small vesiculose cell spaces by short, 

 transverse leaflets extending from one lamella to the other, and 

 filling the calycinal interstices up to the outer margins. The cen- 

 tral area (formed by the bottoms of the cell cups) is transversely sep- 

 tate by continuous simple diaphragms, or by compound plates 

 formed of several convex, anchylosed pieces ; these diaphragms 

 are also intersected by the radial lamellae reaching to the centre, 

 or gradually vanishing in the middle. Surface of vertical lamellae 

 either smooth or granulose, with entire or with denticulated edges. 

 Many species of Cyathophyllum have the side faces of their 

 lamellae decorated by low, equidistant carinae, ascending in a curve 

 from below and outward to the upper and inner edges, where they 

 terminate as acute denticulations, or have the form of transverse 

 trabeculae, the carinae of both sides of the leaves being coincident. 



