126 LOWER PENINSULA. 



the outer and inner area. Found in association with fossils of 

 the corniferous limestone, in the drift deposits of Michigan. 



Plate XLVL, Upper tier, right-hand figure. — Diphyphyllum 

 (Eridophyllum) Vcrneuilli, a species with stems intermediate in 

 size between this form and Diphyphyllum Simcoense, is likewise 

 not uncommon in the drift boulders belonging to the corniferous 

 limestone formation. Its central area, formed of smooth transverse 

 diaphragms, is defined from the peripheral cycle by an internal wall, 

 more or less distinctly developed. Not figured. 



DIPHYPHYLLUM ARCHIACI, Billings. 

 Synon., ERIDOPHYLLUM STRICTUM (?) Milne-Edwards. 



Cylindrical stems, multiplying by calycinal gemmation, with a 

 diameter of from one to two centimeters, transversely wrinkled by 

 fine striae of growth and longitudinally ribbed by septal rugae ; in 

 some specimens the stems are articulated by abrupt constrictions, 

 and moderately distant ; in others the growth is more uniform 

 and the stems are in closer approximation, partly touching with 

 their sides. Calyces generally bell-shaped, with steep sides and 

 gently dilating margins ; sometimes more shallow and of ex- 

 panded form. Lamellae crenulated by the ends of the arched 

 carinae decorating their sides, fifty to sixty in the circumference of 

 a calyx, subequal near the margins, but alternately longer and 

 shorter ; the longer ones abut against a narrow inner wall formed 

 like a horseshoe, which incloses flat transverse diaphragms ; the 

 aperture of the horseshoe is coincident with the principal septal 

 gap. The interstices of the peripheral cycle of lamellae are divided 

 into small cellulose spaces by transverse vesiculose plates. Occurs 

 in the upper Helderberg limestones of Michigan and Ohio, and in 

 the Hamilton group of Thunder Bay ; likewise in Bosanquet town- 

 ship, Canada. The specimens from different localities vary some- 

 what, but agree in general so well that a specific distinction can not 

 be made with propriety. The Helderberg form, which I have identi- 

 fied with this species, is probably the same with Eridophyllum 

 strictum, Milne-Edwards. 



Plate XLVIL, Upper tier. — The left-hand figure is a polished 



