14 GEOLOUICAL AND NATURAL HISTOUY SUllVEY OF CANADA. 



being dopondont upon the size, number and distribution of the interstitial 

 cellSi The spaces between the larger cells (including those above the 

 average size) are occupied by triangular, sometimes sub-rhomboidal, 

 interstitial cells, which are very regularly distributed. 



In longitudinal sections the larger tubes are seen to be crossed by a few 

 horizontal, ineqiiidistant, often slightly curved, and frequently very oblique 

 diaphragms, which become more numerous near the surface of the 

 zoarium. In the smaller tubes the diaphragms are straight, horizontal 

 and very close-set. Small but distinct spiniform tubuli are present at the 

 angles of the interstitial cells, sometimes giving rise to a slight inflation 

 of the walls where they occur. 



The species to which this is most nearly allied is Diplotryi^^a IliUeri, 

 TJlrich, of the Niagara group, of Osgood, Indiana ; but it differs therefrom 

 (1) in possessing spiniform tubuli, (2) in the diaphragms of the smaller 

 tubes being relatively much more numerous than those of the large ones, 

 as compared with that species. 



fjOcaUty and Formation. — Ottawa City. Trenton Formation. 



Collector.— T, C. Weston. 



DlPLOTRYPA WlIITEAVESII, Nicholson. 



Moniiculipora {Dlplotrypa) Whiteavesii, Nicholson. "The genus Monticuli- 

 pora," p. IGO, fig. 31, 1881. 



Locality and Formation. — Somewhat rare in the Trenton formation of 

 Ottawa City. Dr. Nicholson states that this species is *' not uncommon 

 in the Trenton limestone of Peterboro', Ontario, in association with 

 Frasopora Selicyniiy Nich." 



CoUeoior.—T. C. Weston. 



MoNOTRYPA, Nicholson. 



''Irregular, hemispherical or globular masses. Surface smooth, or 

 with low monticules carrying groups of larger cells than the average. 

 Tubes thin-walled, prismatic, and traversed by straight diaphragms. No 

 interstitial cells nor spiniform tubuli. Trenton to Carboniferous." (E. O. 

 Ulrich, Journ. Cincinnati Soc. Nat. Hist., Yol. V., p. 153, 1882.) 



MONOTRYPA UNDULATA, Nicholson. 



Monticulipora (Monoirypa) itndulafa, Nicholson. ^^The genus Monticuli- 

 pora," p. 170, figs. 32 and 33, 1881. 



locality and Formation. — This species, which is the type of the genus 

 is described by Dr. Nicholson as ''rare in the Trenton Limestone of 



