Cretaceous Species of Podoseri.s, Dane. 35 



geneva which have the synaptieulce without any junction- 

 lines, and they blend without lines of union. These are 

 true (eclite) synapticulse. Pratz, following Milaschewitsch, 

 gave some excellent figures of the kinds of synapticulai {op. 

 cit. pi. ix. figs, 1 dy ,12 a, 13 a, and 14 a), and quoted his 

 predecessor's remark that it is necessary to distinguish be- 

 tween the kinds of synapticulai in classification. All the 

 descriptions of these authors are excellent, and nothing can be 

 more true than Pratz's delineations ; but, as was shown after 

 the publication of their essays, the modern example fails to 

 substantiate the value of the distinctions between the kinds 

 of synapticulee (Duncan, 1884, Journ. Linn Soc, Zool. 

 vol. xvii. p. 146), and, moreover, the microscopic investiga- 

 tion of Siderastnca and of a true Tertiary Thamnastrasan 

 leads to the same result as the study of Fangia ; that is to 

 say, as both kinds of synapticulte are found in the same speci- 

 men of a species, and the difference between the kiuds o£ 

 structures is of no physiological importance, the distinction 

 between so-called true and false synapticulaj is of no classifi- 

 catory value. 



The synapticulre in Podosens are therefore both tliick and 

 thin, long and short, and are long from without inwards and 

 obliquely placed upon the flanks of opposed septa, which they 

 unite. This last kind is a feeble representative of the synapticulfB 

 of the recent Fungia, and as in that genus the upper and the 

 lower synapticulas form the roofs and bases of so many oblique 

 canals in regular succession. The delicate dissepiments inter- 

 fere with the continuity of the lumen of the canals. 



27ie Epitheca. — This structure varies in amount according 

 to the height of the corallum. When the coral is low and 

 plano-convex the epitheca is scanty or absent, and it exists 

 over more or less of the costge close to the periphery. But 

 Avhen the coral is tall the cylindrical or nipped-in stem above 

 the attached base is covered with epitheca np to varying 

 heights, but usually to the calicular margin. The epitheca is 

 thin, moulded as it were to the outer edges of the costoe and 

 to their interspaces ; it is more or less granular, and it must 

 have prevented any watery connexion between the synap- 

 ticular canals and the surrounding medium. 



There is no epitheca on the attached base, but the lower 

 surfaces of the septo-costge are in contact with the foreign 

 body supporting the coral, and the synapticulse may be seen 

 to exist between the septa in concentric rows. The coral 

 appears never to have been free. 



In the very interesting young form the low septa and two 

 concentric series of synapticula^ form all the coral. 



