GENERAL HISTORY. ii 



impossible to form any opinion as to their true nature by a 

 mere perusal of the descriptions which are given of them, or 

 an examination of the figures by which they are accompanied. 

 No observer, therefore, who had not access to Eichwald's 

 original specimens, could hope to arrive at any conclusion as to 

 even the generic affinities of most of the above — to say nothing 

 of their value as species. The most of them (excluding C. 

 radians, Fischer) would seem to be probably Monticiiliporce, 

 while the form described as C. annnlatus looks like a Polyzoon, 

 but would seem from Dybowski's description (Die Chaete- 

 tiden, p. 86) to be a Monticuliporoid. This is probably the 

 utmost that could be safely asserted. 



The genus Orbipora, Eichw., is defined as having a discoid 

 corallum, convex above and flat below, composed of vertical 

 cylindrical tubes. The calices are said to be oval below and 

 hexagonal above, all of them equal in size. Tabulae are said 

 to be wanting or rudimentary ; multiplication is by gemmation, 

 and there is a basal epitheca. The species described under 

 this head are Orbipora distinct a, Eichw., and O. fungiformis, 

 Eich. ; but neither could be identified by the descriptions or 

 figures which are given, unless the observer possessed authen- 

 tic specimens to refer to. All that can be stated is, they 

 appear to be discoid forms of Monticulipora. It will be ob- 

 served, however, that in his definition of Orbipora, Eichwald 

 brings forward one structural character (namely, the absence or 

 rudimentary condition of the tabulae), which, if confirmed, and 

 if found to be associated with other structural peculiarities, 

 might possibly afford some justification for the revival of the 

 generic title. 



The genus Dia7iulites, Eichw. (Leth. Ross., p. 487), is de- 

 fined as having an obconical, attenuated, gemmiparous, and 

 ramose corallum, which is fixed by its base, and covered with 

 a thick epitheca below. The corallum is composed of vertical 

 tabulate tubes, which diverge irregularly from the base, and 

 are surrounded by a spongy " coenenchyma." The sides of 

 the corallum are largely grooved, with transverse sulci, indi- 



