130 Cincinnati Society of Natural History. 



preserved specimens of inorusting species ; these present a narrow strip 

 of membrane beyond the range of the cells. This strip is especially 

 well marked in Petigopora, Ulrich. There is therefore this primary 

 difference between the epithecal membrane of the Monticuliporoids, 

 and that of the species of Favosites mentioned; that while in the 

 former it is developed in advance of the marginal cells, in the latter it 

 is formed after the death of the corallites which it covers. Save under 

 the expanded base for attachment, no epitheca is developed in the 

 frondescent and ramose species; but in the laminar or double-leaved 

 and in crusting types, it is always present. In the double-leaved 

 species (e. g., Peronopora decipiens, Rominger), the tubes of each 

 leaf rest upon its own separate epitheca, which is thin, and somewhat 

 wrinkled, as is shown in specimens split between the two epithecal 

 membranes. In the thoroughly incrusting t} r pes the epitheca is 

 excessiveh' thin, while in such partially attached species as Prasopora 

 cincinnatiensis, James, it is thick and strongly wrinkled. 



In the following section of my article 1 must frequently refer to the 

 t} T pe of the genus Monticulipora, and as some difference of opinion 

 exists in the determination of the species really entitled to that claim, 

 I have thought it advisable to briefly point out my reasons for con- 

 sidering Dr. Nicholson's identification of the type species as errone- 

 ous; and I will endeavor to show that the identification of M. mam- 

 mulata, IVOrb., must not, in the meanwhile, "remain a matter of indi- 

 vidual preference or individual opinion." 



The first species given under D'Orbign} T 's description of his genus 

 Monticulipora, is his M. mammulata, from the Lower Silurian of Ohio. 

 This species, must, therefore, be accepted as the t} T pe of the genus. 

 Nicholson, in his various publications on the genus, has identified a 

 common species from Cincinnati with the M. mammulata of D'Orb. 

 The form he has so identified, I believe, is the M. frondosa. of the 

 same author. The specimen mentioned by Nicholson in his " Genus 

 Monticulipora," near the bottom of page 107, I see little difficult}' in 

 recognizing as an example of the common large variety of M. filiasa, 

 described by D'Orbign}' at the same time with the two preceding spe- 

 cies. Nicholson, on page 108 of the work cited, proceeds to give his 

 reasons for his selections of the t} T pe of the genus, but subsequently 

 he freely admits that his selection was an entirely arbitrary one. He 

 remarks: "The difficulties which environ this question arise from 

 the fact that there are at least three, possibl} r four, distinct structural 



