9 



part of another tube, and only appearing on the surface of the colony with their 

 distal parts, but while in most Cyclostomata the distal part of each zooecium keeps 

 its character as a narrow cylindrical tube whether it projects with a shorter or 

 longer free end or only with its frontal convex surface, I have hitherto only found 

 this to be the case in a single species of this division, namely in Meliceritites Doll- 

 fussi Perg. (pi. IV, fig. 23, pi. V, figs. 9, 10.) in which the zooecia are provided with a 

 shorter or longer freely projecting terminal part. As a rule the superficial or ter- 

 minal part of the zooecia enlarges into a rather broad hexagonal, rhombic or qva- 

 drangular area, the zooecial area, and the single areas are in most cases divided 

 from each other by a meshwork of distinct ridges. These areas are very much like 

 those found in the coilostegous Cheilostomata, for inst. in Ongchocella, Micropora, 

 Membranicellaria and Cellnhtria (Cellaria), and Roemer") therefore says: »Gleiche 

 Zellenbildung findet sich auch bei Escharwi. The greatest likeness these areas show 

 to those found in the genus Cellularia as has been pointed out in the historical in- 

 troduction, but this likeness is a quite superficial one as in this genus the meshwork 

 of ridges has nothing to do with the dividing walls and do not correspond to the 

 single zooecia which have a quite dilTerent form=). hi the Melicerlitidae contrary 

 the ridges are the edges of the walls dividing the single zooecial areas which may 

 easily be seen by grinding away a part of the surface of the colony, there being 

 left a system of hollows corresponding in size to the single areas. This meshwork 

 of ridges which is only absent in some species presenting a convex surface, f. inst. 

 in Meliceritites micropora (pi. Ill, fig. 10), is very often in the points of intersection 

 l)rovided with more or less prominent tubercles the presence and development of 

 which is dependent on the manner in which the concave surfaces of the zooecial 

 areas join the marginal ridges. The more the transition of the surface into the 

 ridge is a gradual one the more developed are the tubercles (pi. II, figs. 10, 11,23, pi. 

 Ill, fig. 17) while on the contrary they are feebly developed or quite lacking in such 

 species (pi. Ill, fig. 20, pi. V, figs. 1, 7, 9, 12.) where the ridge is more distinctly defined 

 from the surface. While two contiguous concave surfaces gradually rising towards 

 each other must form a roof-shaped ridge, three or four must where they meet, 

 form a pyramid, but only in a few cases the single surfaces of these pyramids are 

 distinctly defined (pi. V, fig. 19.) being generally rounded. In the circumference of 

 an hexagonal area (pi. II, fig. 11) there can be found six tubercles three of which 

 may be called »praeoral« being placed immediately distally to an aperture while 

 the other three each of which has its place between two apertures may be called 

 »interoral«. When the zooecial areas are rhombic there can only be found prseoral 

 tubercles. 



While concave or saddle-shaped zooecial areas surrounded by distinct ridges 

 and sometimes provided with more or less distinct tubercles are also present in a 

 number of cyclostomatous species, f. inst. in Peripora pseadospiralis Mich., Spiropora 



') 6, p. 18. ■-) 18, p. 209— 212, pis. VII VIU. 



n. Ev, I) Vidensk. Selsk. Skr., 7. R:ukke. naturvidensU. og mathem. Afd. X. 1. 



