MADREPORARIA PERFORATA. 32 1 



f. Lastly, the skeleton in Syringopora and its allies is never 

 composed of spicules, as it is in Tubipora, but its microscopic 

 structure agrees precisely with that of the corallum in the Madre- 

 poraria generally. 



It should be added, however, that though it would appear highly 

 probable that the real affinities of the Syringoporidce. are with the 

 Madreporaria, the members of this family show a resemblance to 

 the Alcyonarians in the fact that their common mode of increase is 

 by stolonal or basal gemmation, and in this respect they differ 

 altogether from the typical Perforate Madreporarians ; though this 

 single feature cannot be allowed to counterbalance their numerous 

 and striking points of resemblance to the FavositidcE. 



The typical genus of the Syri?igoporidce is Syringopora itself, in which 

 the corallum commences as a prostrate network of tubes, resembling in 

 form a colony of Aulopora. In process of growth, this basal network 

 sends up numerous vertical, flexuous, cylindrical corallites, which are not 

 in direct contact, though sometimes {e.g., in S. laxata) they become 

 directly united here and there. The corallites are enclosed, each, in a 

 thick proper wall, and they are usually united by hollow cylindrical con- 

 necting-processes (figs. 204-207) which occasionally {e.g., in S. tabulatd) 

 assume the form of horizontal laminar floors. These connecting-processes 

 place the visceral chambers of adjoining tubes in direct communication, 

 and, as shown in thin sections (fig. 208), they are traversed by con- 

 tinuations of the endothecal tissue of the polypes themselves. The septa 

 are sometimes nearly obsolete, but they usually have the form of vertical 

 rows of calcareous spines. The tabulae are well developed, and are in 

 general more or less regularly funnel-shaped (fig. 208, a), and give rise 

 by their invagination to a more or less continuous tube occupying the 

 axis of the visceral chamber. The species of Syringopora are abundant 

 in the Silurian, Devonian, and Carboniferous deposits, and often reach 

 a large size. 



In the Silurian genus Cannapora, the general form of the corallum is 

 like that of Syringopora, but when connecting-processes are present 

 these are very short, and the corallites are usually partially in contact, 

 in which case they assume a polygonal form and are perforated by mural 

 pores. The tabulae are sometimes funnel-shaped, sometimes simply 

 curved, and the septa are spiniform. 



We may also include in this family the remarkable Devonian genus 

 Chonostegites, which proves to be a link between the Syringoporidce 

 and Favositidce, and has, indeed, been included in the latter family. 

 The corallum in this genus is massive, and is composed of cylindrical 

 corallites which may be partially in contact, but are usually separate 

 and are connected by numerous close-set, concentrically disposed, hori- 

 zontal connecting-floors or laminar expansions. These periodic floors 

 are so far exothecal that they are extensions from the walls of the coral- 

 lites, but they are hollow, and are filled with prolongations of the en- 

 dothecal tissues of the corallites themselves, so that they place the 

 visceral chambers of contiguous tubes in direct communication. In 

 places, the corallites come into direct contact, and in this case their 

 visceral chambers communicate by mural pores precisely similar to 

 those of the Favositidce. The septa have the form of rows of cal- 

 careous spines, and the tabulae differ from those of Syringopora and 



vol. 1. x 



