122 



Cincinnati Society of Natural History. 



terms used to designate the various parts of these Bryozoa: The term 

 zoarium is used to designate the entire colony ( Polyzoarium, Co&nce- 

 cium, etc.) The term frond, I have sometimes used in an equivalent 

 sense, in describing species of Ptilodictya, Fenestella, etc. In speak- 

 ing of the external characters the true cells are called simply cells ; in 

 describing the internal characters, of the tubular forms, the same are 

 termed tubes. Interstitial cells and interstitial tubes are used in the 

 same way to distinguish the more irregular, and usually smaller pores 

 situated between and often completely 7 surrounding the true cells. In- 

 terstitial pits, I have called the shallow interstitial cells found in some 

 of the Ptilodictyonidce. These are well developed in Stictoporella, 

 nov. gen. The axial tube is the central cavity in such forms as are 

 afterwards described under Cazloclema. The tube is lined with an 

 epitheca (Axenrohr, Dybow.) The spiniform tubli are equivalent to 

 the "spiniform corallites'' of Nicholson, and the " Wandrohrchen" of 

 Dybowski. Connecting foramina is a term applied to the minute 

 pores in the walls of the tubes, by means of which contiguous cells are 

 connected. These are found in numerous Biwozoa, and probably ex- 

 isted in many of the Ptilodictyonidce, and at least some of the Monti- 

 culiporidoe. The straight plates (tabulae) crossing the tubes are called 

 diaphragms. The convex plates which line one side of the tubes as in 

 Monticulipora, or both sides, as in Prasopora, 1 have termed cystoid 

 diaphragms. 



In Fistulipora, Crepipora (nov. gen.), and other genera, are found 

 small spots ("maculse") produced by an aggregation of the interstitial 

 cells. They are usually depressed below the general surface. The 

 " monticules" are usually constituted b} 7 groups of larger-sized cells 

 than the average, which are elevated above the general surface. 



GENERAL STRUCTURE. 



1. Form of the Zoarium. — In the mode of growth of the zoarium, 

 and the form ultimately assumed by the^colonv, we find great varia- 

 tions. B}' this is not meant that individual species are specially 

 variable in shape, for nearly all exhibit a tolerably constant form 

 when adult, and sometimes even all the forms placed in a genus may 

 adhere more or less strictly to some particular method of growth. 



The zOarium of the Monticuliporidce and Fistuliporidoi, usually 

 exhibits one Or other of the following conditions : 



1. The simply massive zoarium, of which Monotrypa undulata^ 

 Nicholson, is a good example. 



