APPENDIX. 



233 



author of the genus or by any other observer. Judging from the de- 

 scriptions and figures which Dybowski has given of the forms which he 

 has included under the name of Trcmatopora, Hall, it seems safe, how- 

 ever, to conclude that we have to deal here with a peculiar type of 

 Monticuliporoids, which differ in important respects from all the forms 

 which have been described in the preceding portion of this work. 

 From the brief diagnosis above given, and the accompanying engrav- 

 ing (fig. 48), it will be seen that these types possess a dimorphic coral- 

 lum, composed of large and small corallites, which differ both in size 

 and in their internal structure, while a third series of corallites is repre- 

 sented by an abundance of "spiniform corallites." The large coral- 

 lites are oval, with thick lamellar walls (fig. 48, a), and with a very 



Fig. 48. — A, Tangential s&ci\onoi Trcmatofora colltculata, Eichw. (Dyb.), enlarged, showing 

 the large tubes surrounded by small angular corallites, and having "spiniform corallites " 

 developed close beside them ; B, Outer portion of a transverse section of the same, where 

 the tubes are cut longitudinally, enlarged, showing the large corallites, with their few and 

 remote tabula, and the closely tabulate interstitial corallites. From the Lower Silurian 

 of Russia. (Copied from Dybowski.) 



small number of complete horizontal tabular (fig. 48, b). The small 

 corallites are numerous, angular in shape, with imperfect walls, and 

 with very numerous, close-set, horizontal tabulae (fig. 48, c), which may 

 become more or less vesicular. On the lateral margins of each of the 

 large corallites are also developed two or three conspicuous " spiniform 

 corallites." The interstitial corallites, lastly, are present in such num- 

 bers as to completely isolate the large tubes, two or three rows of the 

 former seeming usually to intervene between any given pair of the 

 latter. 



As to the af^nities of the forms included by Dybowski under the 

 head of Trcmatopora, Hall, they differ from all the species of Hctcro- 

 trypa, Nich., in the fact that the large corallites are completely isolated 

 from one another by the development of an excessive number of inter- 

 stitial corallites. On the other hand, while they resemble the species 

 of Fistidipora, M'Coy, in the fact just mentioned, they are fundamen- 

 tally distinguished from these by the great thickening of the walls of 



