Il8 LOWER PENINSULA. 



bracing one another in their superposition, but not always com- 

 bining with their edges into uninterrupted vertical leaves. The 

 interlamellar interstices are traversed by transverse plates, and 

 divided into cellulose spaces, but the dissepiments are not inde- 

 pendent vcsiculose leaflets ; they make part of the tent-shaped folds 

 of the invaginated series of cell cups, and represent the rounded, 

 outwardly directed flexion of the plicated cup walls, while the in- 

 wardly turned folds are sharply crested. Root-like, cylindrical ex- 

 crescences from the side walls of the polyparia, by which they are 

 attached to other bodies, are a peculiarity of the different species of 

 Omphyma, which, however, are not exclusively so to them, but are 

 also noticed in other forms of the Cyathophylloid family. As 

 another distinctive character of Omphyma, the development of four 

 septal foveae is mentioned by Milne-Edwards, but they are generally 

 not all equally distinct, while very frequently only one of them is 

 obvious, the others being almost obsolete. The genus Ptycho- 

 phyllum, described by Milne-Edwards as being organized like 

 Chonophyllum, differing from it in the twisted converging ends of 

 the radial lamellae, forming a central false columella, is likewise in 

 close structural relationship with Omphyma, and in the special 

 case of Ptychophyllum Stockesii, I found its aflfinity with Om- 

 phyma verrucosa so great that I altered the name of the first from 

 Ptychophyllum to Omphyma. 



OMPHYMA VERRUCOSA, Milne-Edwards. 



Conical polyparia, attaining in larger specimens the length of 

 one decimeter by a calyx diameter of from seven to eight centi- 

 meters. Surface of the silicified specimens generally exfoliated ; if 

 perfect, it is covered by an epithecal wall with annular wrinkles of 

 growth, and longitudinally striate by septal furrows. From the 

 sides of the conical walls numerous cylindrical, root-like prolon- 

 gations grow out, serving for attachment of the coral to other 

 bodies ; these appendices were not distributed equally over the sur- 

 face, but seemed to form only on those sides where a chance for 

 attachment was offered by close proximity of an object. Calyces 

 spacious, with steeply ascending sides and a gently expanded mar- 

 gin ; bottom broad, convex, with depressed circumference, flat or 

 somewhat concave in the centre, w^hich may be almost smooth, or 



