76 LOWER PENINSULA. 



In some specimens the constrictions are not so deep as in others, and 

 the tubes then come in more intimate contact with their sides, which 

 in such case communicate by lateral pores, and fully resemble the 

 tubes of an ordinary form of Michelinia. The tubes are transversely 

 intersected by interlacing vesiculose diaphragms of compound 

 structure ; the channel walls longitudinally striate by furrows and 

 rows of spinules, conformable with the structure of Michelinia. 



Occurs frequently in the drift of Michigan, and is common in the 

 corniferous limestone of Canada and New York ; it is rarely seen at 

 the Falls of the Ohio, where Michelinia cylindrica, a closely related 

 form., is abundant. 



Plate XXVIII. — Figs. 3 and 4 represent aside view and a surface 

 view of silicified specimens. 



HALYSITIN.E. 



Colonies of tubular polyp cells, multiplying by lateral gemmation, 

 radiated by a cycle of twelve longitudinal crests or rows of spinules, 

 and transversely septate by diaphragms of variable form, straight 

 or funnel-shaped. The tubes are either free, loosely attached to 

 each other, or laterally connected into laminar rows, or again dis- 

 tant and connected by short transverse branches, sometimes in- 

 discriminately anchylosed into irregular conglomerated masses. 

 The subordinate genera are Halysites, Syringopora, Cannapora, and 

 Aulopora. 



HALYSITES, Fischer. 

 Catenipora, Lamark. 



Elliptical tubes, intimately connected at their lateral edges into 

 chain-like single rows, which form erect laminar expansions, bent 

 into tortuous curves, and composing, by the mutual junction and 

 intersection of the laminae, a network of irregular loops. Tubes 

 radiated by twelve longitudinal crests, and transversely septate by 

 closely set flat diaphragms. No lateral connection between the 

 tubes by pores. 



